Add EXP labels to SKR pins

Marlin/src/pins/lpc1768/pins_BTT_SKR_V1_3.h

  *               -----                                              -----
  *               EXP2                                               EXP1
  */
+
+#define EXP1_1_PIN          P1_30
+#define EXP1_2_PIN          P1_18
+#define EXP1_3_PIN          P1_20
+#define EXP1_4_PIN          P1_22
+#define EXP1_6_PIN          P0_28
+#define EXP1_7_PIN          P1_19
+#define EXP1_8_PIN          P1_21
+#define EXP1_9_PIN          P1_23
+
+#define EXP2_1_PIN          P0_17
+#define EXP2_2_PIN          P3_26
+#define EXP2_3_PIN          P3_25
+#define EXP2_4_PIN          P1_31
+#define EXP2_6_PIN          P0_15
+#define EXP2_7_PIN          P0_16
+#define EXP2_8_PIN          P0_18
+#define EXP2_9_PIN          -1
+
 #if HAS_SPI_LCD
 
   #if ENABLED(ANET_FULL_GRAPHICS_LCD)
     *                   LCD                             LCD
     */
 
-    #define LCD_PINS_RS    P1_23
+    #define LCD_PINS_RS    EXP1_9_PIN
 
-    #define BTN_EN1        P1_20
-    #define BTN_EN2        P1_22
-    #define BTN_ENC        P1_18
+    #define BTN_EN1        EXP1_3_PIN
+    #define BTN_EN2        EXP1_4_PIN
+    #define BTN_ENC        EXP1_2_PIN
 
-    #define LCD_PINS_ENABLE P1_21
-    #define LCD_PINS_D4    P1_19
+    #define LCD_PINS_ENABLE EXP1_8_PIN
+    #define LCD_PINS_D4    EXP1_7_PIN
 
   #elif ENABLED(CR10_STOCKDISPLAY)
 
-    #define LCD_PINS_RS    P1_22
+    #define LCD_PINS_RS    EXP1_4_PIN
 
-    #define BTN_EN1        P1_18
-    #define BTN_EN2        P1_20
-    #define BTN_ENC        P0_28   // (58) open-drain
+    #define BTN_EN1        EXP1_2_PIN
+    #define BTN_EN2        EXP1_3_PIN
+    #define BTN_ENC        EXP1_6_PIN   // (58) open-drain
 
-    #define LCD_PINS_ENABLE P1_23
-    #define LCD_PINS_D4    P1_21
+    #define LCD_PINS_ENABLE EXP1_9_PIN
+    #define LCD_PINS_D4    EXP1_8_PIN
 
   #else // !CR10_STOCKDISPLAY
 
-    #define LCD_PINS_RS    P1_19
+    #define LCD_PINS_RS    EXP1_7_PIN
 
-    #define BTN_EN1        P3_26   // (31) J3-2 & AUX-4
-    #define BTN_EN2        P3_25   // (33) J3-4 & AUX-4
-    #define BTN_ENC        P0_28   // (58) open-drain
+    #define BTN_EN1        EXP2_2_PIN   // (31) J3-2 & AUX-4
+    #define BTN_EN2        EXP2_3_PIN   // (33) J3-4 & AUX-4
+    #define BTN_ENC        EXP1_6_PIN   // (58) open-drain
 
-    #define LCD_PINS_ENABLE P1_18
-    #define LCD_PINS_D4    P1_20
+    #define LCD_PINS_ENABLE EXP1_2_PIN
+    #define LCD_PINS_D4    EXP1_3_PIN
 
-    #define LCD_SDSS       P0_16   // (16) J3-7 & AUX-4
-    #define SD_DETECT_PIN  P1_31   // (49) (NOT 5V tolerant)
+    #define LCD_SDSS       EXP2_7_PIN   // (16) J3-7 & AUX-4
+    #define SD_DETECT_PIN  EXP2_4_PIN   // (49) (NOT 5V tolerant)
 
     #if ENABLED(FYSETC_MINI_12864)
-      #define DOGLCD_CS    P1_18
-      #define DOGLCD_A0    P1_19
-      #define DOGLCD_SCK   P0_15
-      #define DOGLCD_MOSI  P0_18
+      #define DOGLCD_CS    EXP1_2_PIN
+      #define DOGLCD_A0    EXP1_7_PIN
+      #define DOGLCD_SCK   EXP2_6_PIN
+      #define DOGLCD_MOSI  EXP2_8_PIN
 
       #define LCD_BACKLIGHT_PIN -1
 
       #define FORCE_SOFT_SPI      // Use this if default of hardware SPI causes display problems
                                   //   results in LCD soft SPI mode 3, SD soft SPI mode 0
 
-      #define LCD_RESET_PIN P1_20   // Must be high or open for LCD to operate normally.
+      #define LCD_RESET_PIN EXP1_3_PIN   // Must be high or open for LCD to operate normally.
 
       #if EITHER(FYSETC_MINI_12864_1_2, FYSETC_MINI_12864_2_0)
         #ifndef RGB_LED_R_PIN
-          #define RGB_LED_R_PIN P1_21
+          #define RGB_LED_R_PIN EXP1_8_PIN
         #endif
         #ifndef RGB_LED_G_PIN
-          #define RGB_LED_G_PIN P1_22
+          #define RGB_LED_G_PIN EXP1_4_PIN
         #endif
         #ifndef RGB_LED_B_PIN
-          #define RGB_LED_B_PIN P1_23
+          #define RGB_LED_B_PIN EXP1_9_PIN
         #endif
       #elif ENABLED(FYSETC_MINI_12864_2_1)
-        #define NEOPIXEL_PIN    P1_21
+        #define NEOPIXEL_PIN    EXP1_8_PIN
       #endif
 
     #else // !FYSETC_MINI_12864
 
       #if ENABLED(MKS_MINI_12864)
 
-        #define DOGLCD_CS    P1_21
-        #define DOGLCD_A0    P1_22
-        #define DOGLCD_SCK   P0_15
-        #define DOGLCD_MOSI  P0_18
+        #define DOGLCD_CS    EXP1_8_PIN
+        #define DOGLCD_A0    EXP1_4_PIN
+        #define DOGLCD_SCK   EXP2_6_PIN
+        #define DOGLCD_MOSI  EXP2_8_PIN
 
       #elif ENABLED(ENDER2_STOCKDISPLAY)
 
          *               5V | · · | GND
          *     (MOSI) P1_23 | · · | P1_22 (LCD_CS)
          *   (LCD_A0) P1_21 | · · | P1_20 (BTN_EN2)
-         *      RESET P1.19 | · · | P1_18 (BTN_EN1)
+         *      RESET P1_19 | · · | P1_18 (BTN_EN1)
          *  (BTN_ENC) P0_28 | · · | P1_30 (SCK)
          *                   -----
          *                    EXP1
          */
 
-        #define BTN_EN1      P1_18
-        #define BTN_EN2      P1_20
-        #define BTN_ENC      P0_28
-        #define DOGLCD_CS    P1_22
-        #define DOGLCD_A0    P1_21
-        #define DOGLCD_SCK   P1_30
-        #define DOGLCD_MOSI  P1_23
+        #define BTN_EN1      EXP1_2_PIN
+        #define BTN_EN2      EXP1_3_PIN
+        #define BTN_ENC      EXP1_6_PIN
+        #define DOGLCD_CS    EXP1_4_PIN
+        #define DOGLCD_A0    EXP1_8_PIN
+        #define DOGLCD_SCK   EXP1_1_PIN
+        #define DOGLCD_MOSI  EXP1_9_PIN
         #define FORCE_SOFT_SPI
         #define LCD_BACKLIGHT_PIN -1
       #endif
 
       #if ENABLED(ULTIPANEL)
-        #define LCD_PINS_D5 P1_21
-        #define LCD_PINS_D6 P1_22
-        #define LCD_PINS_D7 P1_23
+        #define LCD_PINS_D5 EXP1_8_PIN
+        #define LCD_PINS_D6 EXP1_4_PIN
+        #define LCD_PINS_D7 EXP1_9_PIN
       #endif
 
     #endif // !FYSETC_MINI_12864
 #endif
 
 #if SD_CONNECTION_IS(LCD)
-  #define SS_PIN           P0_16
+  #define SS_PIN           EXP2_7_PIN
 #endif
 
 /**

Marlin/src/pins/stm32/pins_BTT_SKR_E3_DIP.h

 //
 // Servos
 //
-#define SERVO0_PIN         PA1
+#define SERVO0_PIN         PA1    // SERVOS
 
 //
 // Limit Switches
 //
-#define X_STOP_PIN         PC1
-#define Y_STOP_PIN         PC0
-#define Z_STOP_PIN         PC15
+#define X_STOP_PIN         PC1    // X-STOP
+#define Y_STOP_PIN         PC0    // Y-STOP
+#define Z_STOP_PIN         PC15   // Z-STOP
 
 //
 // Z Probe must be this pin
 //
-#define Z_MIN_PROBE_PIN    PC14
+#define Z_MIN_PROBE_PIN    PC14   // PROBE
 
 //
 // Filament Runout Sensor
 //
 #ifndef FIL_RUNOUT_PIN
-  #define FIL_RUNOUT_PIN   PC2
+  #define FIL_RUNOUT_PIN   PC2    // E0-STOP
 #endif
 
 //
 //
 // Temperature Sensors
 //
-#define TEMP_0_PIN         PA0   // Analog Input
-#define TEMP_BED_PIN       PC3   // Analog Input
+#define TEMP_0_PIN         PA0   // Analog Input "TH0"
+#define TEMP_BED_PIN       PC3   // Analog Input "TB0"
 
 //
 // Heaters / Fans
 //
-#define HEATER_0_PIN       PC8   // EXTRUDER
-#define HEATER_BED_PIN     PC9   // BED
-#define FAN_PIN            PA8
+#define HEATER_0_PIN       PC8   // HE
+#define HEATER_BED_PIN     PC9   // HB
+#define FAN_PIN            PA8   // FAN0
 
 //
 // USB connect control
  *                 -----
  *                 EXP1
  */
+#define EXP1_1_PIN         PA15
+#define EXP1_2_PIN         PA9
+#define EXP1_3_PIN         PA10
+#define EXP1_4_PIN         PB8
+#define EXP1_6_PIN         PB6
+#define EXP1_7_PIN         -1
+#define EXP1_8_PIN         PB9
+#define EXP1_9_PIN         PB7
+
 #if HAS_SPI_LCD
-  #define BEEPER_PIN       PA15
-  #define BTN_ENC          PB6
+  #define BTN_ENC          EXP1_6_PIN
+  #define BTN_EN1          EXP1_2_PIN
+  #define BTN_EN2          EXP1_3_PIN
 
   #if ENABLED(CR10_STOCKDISPLAY)
 
-    #define LCD_PINS_RS    PB8
-
-    #define BTN_EN1        PA9
-    #define BTN_EN2        PA10
+    #define BEEPER_PIN     EXP1_1_PIN
 
-    #define LCD_PINS_ENABLE PB7
-    #define LCD_PINS_D4    PB9
+    #define LCD_PINS_RS    EXP1_4_PIN
+    #define LCD_PINS_ENABLE EXP1_9_PIN
+    #define LCD_PINS_D4    EXP1_8_PIN
 
   #elif EITHER(MKS_MINI_12864, ENDER2_STOCKDISPLAY)
 
      *                    EXP1
      */
 
-    #define BTN_EN1      PA9
-    #define BTN_EN2      PA10
-    #define DOGLCD_CS    PB8
-    #define DOGLCD_A0    PB9
-    #define DOGLCD_SCK   PA15
-    #define DOGLCD_MOSI  PB7
+    #define DOGLCD_CS    EXP1_4_PIN
+    #define DOGLCD_A0    EXP1_8_PIN
+    #define DOGLCD_SCK   EXP1_1_PIN
+    #define DOGLCD_MOSI  EXP1_9_PIN
     #define FORCE_SOFT_SPI
     #define LCD_BACKLIGHT_PIN -1
 
   #else
-    #error "Only CR10_STOCKDISPLAY and MKS_MINI_12864 are currently supported on the BIGTREE_SKR_E3_DIP."
+    #error "Only CR10_STOCKDISPLAY, ENDER2_STOCKDISPLAY, and MKS_MINI_12864 are currently supported on the BIGTREE_SKR_E3_DIP."
   #endif
 
 #endif // HAS_SPI_LCD

Marlin/src/pins/stm32/pins_BTT_SKR_MINI_E3.h

  *                 -----
  *                 EXP1
  */
+
+#define EXP1_1_PIN         PB5
+#define EXP1_2_PIN         PA9
+#define EXP1_3_PIN         PA10
+#define EXP1_4_PIN         PB8
+#define EXP1_6_PIN         PB6
+#define EXP1_7_PIN         -1
+#define EXP1_8_PIN         PB9
+#define EXP1_9_PIN         PB7
+
 #if HAS_SPI_LCD
 
   #if ENABLED(CR10_STOCKDISPLAY)
 
-    #define BEEPER_PIN     PB5
-    #define BTN_ENC        PB6
-
-    #define LCD_PINS_RS    PB8
+    #define BEEPER_PIN     EXP1_1_PIN
 
-    #define BTN_EN1        PA9
-    #define BTN_EN2        PA10
+    #define BTN_EN1        EXP1_2_PIN
+    #define BTN_EN2        EXP1_3_PIN
+    #define BTN_ENC        EXP1_6_PIN
 
-    #define LCD_PINS_ENABLE PB7
-    #define LCD_PINS_D4    PB9
+    #define LCD_PINS_RS    EXP1_4_PIN
+    #define LCD_PINS_ENABLE EXP1_9_PIN
+    #define LCD_PINS_D4    EXP1_8_PIN
 
   #elif ENABLED(ZONESTAR_LCD)     // ANET A8 LCD Controller - Must convert to 3.3V - CONNECTING TO 5V WILL DAMAGE THE BOARD!
 
     #error "CAUTION! ZONESTAR_LCD requires wiring modifications. See 'pins_BTT_SKR_MINI_E3.h' for details. Comment out this line to continue."
 
-    #define LCD_PINS_RS    PB9
-    #define LCD_PINS_ENABLE PB6
-    #define LCD_PINS_D4    PB8
-    #define LCD_PINS_D5    PA10
-    #define LCD_PINS_D6    PA9
-    #define LCD_PINS_D7    PB5
+    #define LCD_PINS_RS    EXP1_8_PIN
+    #define LCD_PINS_ENABLE EXP1_6_PIN
+    #define LCD_PINS_D4    EXP1_4_PIN
+    #define LCD_PINS_D5    EXP1_3_PIN
+    #define LCD_PINS_D6    EXP1_2_PIN
+    #define LCD_PINS_D7    EXP1_1_PIN
     #define ADC_KEYPAD_PIN PA1    // Repurpose servo pin for ADC - CONNECTING TO 5V WILL DAMAGE THE BOARD!
 
   #elif EITHER(MKS_MINI_12864, ENDER2_STOCKDISPLAY)
      *                   -----
      *                    EXP1
      */
-    #define BTN_EN1        PA9
-    #define BTN_EN2        PA10
-    #define BTN_ENC        PB6
-
-    #define DOGLCD_CS      PB8
-    #define DOGLCD_A0      PB9
-    #define DOGLCD_SCK     PB5
-    #define DOGLCD_MOSI    PB7
+    #define BTN_EN1        EXP1_2_PIN
+    #define BTN_EN2        EXP1_3_PIN
+    #define BTN_ENC        EXP1_6_PIN
+
+    #define DOGLCD_CS      EXP1_4_PIN
+    #define DOGLCD_A0      EXP1_8_PIN
+    #define DOGLCD_SCK     EXP1_1_PIN
+    #define DOGLCD_MOSI    EXP1_9_PIN
     #define FORCE_SOFT_SPI
     #define LCD_BACKLIGHT_PIN -1