Where is this "extremely well documented process" to enroll new signing keys on an embedded device? I don't see one for any of these embedded processors with secure boot.

https://pip-assets.raspberrypi.com/categories/1214-rp2350/do...

https://documentation.espressif.com/esp32_technical_referenc...

https://docs.amd.com/v/u/en-US/ug1085-zynq-ultrascale-trm