rpi
https://github.com/BrianSidebotham/arm-tutorial-rpi
https://github.com/brianwiddas/pi-baremetal
https://github.com/mrvn/RaspberryPi-baremetal
https://github.com/Pikrass/pios
https://github.com/jxcodetw/rpi2-arm-bare-metal
https://github.com/madotuki/rpi2-baremetal
https://github.com/jeffreyantony/multipi
https://github.com/xinu-os/xinu
https://github.com/zhiyihuang/xv6_rpi_port
https://github.com/houcheng/xv6-armv7
https://github.com/sudharson14/xv6-OS-for-arm-v8
bpi
https://github.com/keesj/A13-OlinuXino-playground
https://github.com/allwinner-zh/bootloader
https://github.com/hno/allwinner-boot
https://github.com/cubieboard/a20-boot
https://github.com/skristiansson/ar100-info
https://github.com/neokeld/baremetalOS
https://github.com/siemens/jailhouse