Open source VPU side bootloader for Raspberry Pi.
OTHER License
FlashDB BSP for auto test
ATF for Pine64 (historical project, use https://github.com/longsleep/arm-trusted-firmware instead)
"Das U-Boot" Source Tree
C++ library for programming the VideoCore GPU on all Raspberry Pi's.
Tutorial: Writing a "bare metal" operating system for Raspberry Pi 4
A tiny C header-only risc-v emulator.
The Interim Operating System
A bare metal programming guide (ARM microcontrollers)