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 se

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/documents/RP-008373-DS-2-rp2350-datasheet.pdf?disposition=inline https://pip-assets.raspberrypi.com/categories/1214-rp2350/do... https://documentation.espressif.com/esp32_technical_reference_manual_en.pdf https://documentation.espressif.com/esp32_technical_referenc... https://docs.amd.com/v/u/en-US/ug1085-zynq-ultrascale-trm https://docs.amd.com/v/u/en-US/ug1085-zynq-ultrascale-trm