Move SOFT_SERIAL_PIN to data driven (#19863)

keyboards/handwired/brain/config.h

@@ -42,11 +42,6 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #define MOUSEKEY_MAX_SPEED 7
 #define MOUSEKEY_WHEEL_DELAY 0
 
-/* Set 0 if debouncing isn't needed */
-
-
-/* serial.c configuration for split keyboard */
-#define SOFT_SERIAL_PIN D0
 #define EE_HANDS
 
 //#define SPLIT_HAND_PIN B7

keyboards/handwired/brain/info.json

@@ -12,6 +12,7 @@
         "matrix": [0, 6]
     },
     "split": {
+        "soft_serial_pin": "D0",
         "bootmagic": {
             "matrix": [5, 0]
         }