Re-structure splinky support to handle versioning in the same fashion as for the teensy (#19123)

keyboards/bastardkb/charybdis/3x6/v2/splinky_2/rules.mk

@@ -0,0 +1,37 @@
+# MCU name
+MCU = RP2040
+
+# Bootloader selection
+BOOTLOADER = rp2040
+
+# RP2040-specific options
+ALLOW_WARNINGS = yes
+PICO_INTRINSICS_ENABLED = no # ATM Unsupported by ChibiOS.
+
+# Build Options
+#   change yes to no to disable
+#
+BOOTMAGIC_ENABLE = yes      # Enable Bootmagic Lite
+MOUSEKEY_ENABLE = no        # Mouse keys
+EXTRAKEY_ENABLE = yes       # Audio control and System control
+CONSOLE_ENABLE = no         # Console for debug
+COMMAND_ENABLE = no         # Commands for debug and configuration
+NKRO_ENABLE = no            # Enable N-Key Rollover
+BACKLIGHT_ENABLE = no       # Enable keyboard backlight functionality
+RGBLIGHT_ENABLE = no        # Enable keyboard RGB underglow
+AUDIO_ENABLE = no           # Audio output
+
+AUDIO_SUPPORTED = no        # Audio is not supported
+RGB_MATRIX_SUPPORTED = yes  # RGB matrix is supported and enabled by default
+RGBLIGHT_SUPPORTED = yes    # RGB underglow is supported, but not enabled by default
+RGB_MATRIX_ENABLE = yes     # Enable keyboard RGB matrix functionality
+RGB_MATRIX_DRIVER = WS2812
+
+SPLIT_KEYBOARD = yes
+LAYOUTS = split_3x6_3
+
+POINTING_DEVICE_ENABLE = yes # Enable trackball
+POINTING_DEVICE_DRIVER = pmw3360
+
+SERIAL_DRIVER = vendor
+WS2812_DRIVER = vendor