No, not saw something like that.
But from my point of view it is not necessary, you can look something what is already done. For example mbed-os-bluepill - Bluepill STM32F103C8 support for Mbed OS 6 | Mbed made by @hudakz. It looks simple. When you compared to the standard program for a supported board, new are only files (see end of page) custom_targets.json and files for pinmap configuration (PeripheralPins.c and PinNames.h).