That's great!
It's unfortunately a bit buried, but there the porting guide suggests what a minimal upstream board should support: <
https://book.tockos.org/development/porting#adding-a-platform-to-tock-repository>
1. The hardware must be widely available. Generally that means the hardware platform can be purchased online.
2. The port of Tock to the platform must include at least:
- Console support so that debug!() and printf() work.
- Timer support.
- GPIO support with interrupt functionality.
3. The contributor must be willing to maintain the platform, at least initially, and help test the platform for future releases.
In other words, the blink and hello world apps should work.
GPIO, RCC and UART should be sufficient for this.
Having said that, there is no harm to initiating a draft pull request _or_ sharing an external repo with the port at whatever stage you have if it would be useful to get a gut check that the style and/or implementation details are on the right path.