Unable to set serial driver in json format

[Lefuneste83]

While undergoing some keyboard definition cleanup for a PR on main QMK repo, I have noticed one annoying issue while testing in parallel against vial-qmk codebase.

Using KLOR keyboard on RP2040 ARM MCU

QMK code reviewers ask me to migrate all definitions under json format. While transposing these changes in vial-qmk I notice that one specific and significant setting seems to be lagging behind in the vial-qmk codebase.

I have managed to get rid of all rules.mk entries at keyboard level except for one. I am unable to implement the serial driver to json format.

Rules.mk entry that should be transposable to json:

SERIAL_DRIVER = vendor

Equivalent expected json entry:

    "split": {
        "serial": {
            "driver": "vendor",
            "pin": "GP1"
        },

When implementing this change I get the following error in compilation pre validation
☒ split: Additional properties are not allowed ('serial' was unexpected)

This setting is required as we are moving to a full duplex serial communication between the two keyboard sides and the legacy and outdated soft_serial_pin is not sufficient anymore from the json data structure. A code update on this specific part would be much appreciated.

Thanks!