Changes

Network and USB boot

Support for these additional bootmodes will be added in the future via optional bootloader updates. The current schedule is to release network boot first, then USB boot.

OK, Raspberry Pi Foundation release '''BETA version to support USB boot''' on May. 2202, please refer to [https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2711_bootloader_config.md Pi 4 Bootloader Configuration]

More detail please refer to https://www.raspberrypi.org/documentation/hardware/raspberrypi/booteeprom.md and https://www.raspberrypi.org/documentation/hardware/raspberrypi/bootmodes/msd.md