It had, e.g., a big chunk of code bolted on that
loaded a binary data file at boot time and
configured the various peripherals.
i don't know who you are but we probably both contributed at different times - i was the one who released the first linux and u-boot kernel source to the public via my server, and later on did a usb sniff of the USB-FEL traffic by putting LIVESUIT.EXE into qemu, configuring qemu to give it access to one of the USB ports and uploading an OS to one of my Computer Cards. that was enough for Henrik (hno) and others to complete the fex-boot program. i love doing that stuff.
anyway, upshot is: after a LOT of work by a LOT of people (including yourself it sounds like), the A20 is one of the few china processors that's fully libre reverse-engineered for its boot process, contains no DRM, and even the Video decode engine and 2D GPU are now reverse-engineered.
there aren't very many processors you can say that about - if you do know of any please tell me because i will need to make an in-depth evaluation.