✨ MKS Mini12864 v3 for Robin E3/E3D (#22368)

Marlin/src/pins/stm32f1/pins_MKS_ROBIN_E3_common.h

     #define DOGLCD_MOSI                     PB15
 
   #elif ENABLED(MKS_MINI_12864_V3)
-    #define ENABLE_SPI3
     #define DOGLCD_CS                       PA4
     #define DOGLCD_A0                       PA5
     #define LCD_PINS_DC                     DOGLCD_A0
     #define NEOPIXEL_PIN                    PA7
     #define DOGLCD_MOSI                     PB15
     #define DOGLCD_SCK                      PB13
-
+    #define FORCE_SOFT_SPI
+    #define SOFTWARE_SPI
+    
   #else
 
     #define LCD_PINS_D4                     PA6

buildroot/share/PlatformIO/variants/MARLIN_F103Rx/variant.h

 #endif
 
 // Override default Arduino configuration
+
 // SPI Definitions
-#define PIN_SPI_SS              PA4
-#define PIN_SPI_MOSI            PA7
-#define PIN_SPI_MISO            PA6
-#define PIN_SPI_SCK             PA5
+#if DEFAULT_SPI == 3
+  #define PIN_SPI_SS            PA15
+  #define PIN_SPI_MOSI          PB3
+  #define PIN_SPI_MISO          PB4
+  #define PIN_SPI_SCK           PB5
+#elif DEFAULT_SPI == 2
+  #define PIN_SPI_SS            PB12
+  #define PIN_SPI_MOSI          PB13
+  #define PIN_SPI_MISO          PB14
+  #define PIN_SPI_SCK           PB15
+#else
+  #define PIN_SPI_SS            PA4
+  #define PIN_SPI_MOSI          PA7
+  #define PIN_SPI_MISO          PA6
+  #define PIN_SPI_SCK           PA5
+#endif
 
 // I2C Definitions
 #define PIN_WIRE_SDA            PB7
 #ifndef TIMER_SERVO
   #define TIMER_SERVO           TIM2
 #endif
+
 // UART Definitions
 // Define here Serial instance number to map on Serial generic name
 #define SERIAL_UART_INSTANCE    1
 #define PIN_SERIAL_RX           PA10
 #define PIN_SERIAL_TX           PA9
 
-/* Extra HAL modules */
+// Extra HAL modules
 #if defined(STM32F103xE) || defined(STM32F103xG)
 #define HAL_DAC_MODULE_ENABLED
 #endif

ini/stm32f1.ini

 [env:mks_robin_e3]
 platform                    = ${common_stm32.platform}
 extends                     = common_STM32F103RC
-build_flags                 = ${common_stm32.build_flags}
-  -DDEBUG_LEVEL=0 -DTIMER_SERVO=TIM5
+build_flags                 = ${common_stm32.build_flags} -DDEBUG_LEVEL=0 -DTIMER_SERVO=TIM5 -DDEFAULT_SPI=3
 build_unflags               = ${common_stm32.build_unflags} -DUSBCON -DUSBD_USE_CDC
 monitor_speed               = 115200
 board_build.offset          = 0x5000