https://developer.nvidia.com/linux-tegra-rel-16 Tegra3 aka Surface RT https://developer.nvidia.com/linux-tegra-rel-17 Tegra4 aka Surface RT2
The ContextSwitcher switches back from the windows Bootmgr environment back to the UEFI environment. Good for patch reference for SurfaceRT Grub2 display. Also setup for VisualC https://github.com/imbushuo/boot-shim-tegra-3
I'd also recommend reading Jay Carlson's excellent notes on Embedded Linux here - https://jaycarlson.net/embedded-linux/ as an overview.