Also checkout Tegra Shield Tablet running Ubuntu natively. http://forum.xda-developers.com/shield-tablet/development/ru...
Note that this last bit proprietary blob is only the low-level GPU driver. Linux device-drivers of the other controllers of the Tegra X1 SoC already appear to be available in source form at https://git.kernel.org/cgit/linux/kernel/git/tegra/linux.git... (search for 'Tegra X1' or 'T210' or 'Tegra 210').
Also https://developer.nvidia.com/embedded/linux-tegra contains source-code(with supporting documentation) for the non-kernel parts like for boot-loader(u-boot), OpenCV, OpenGL, X11, Gstreamer and even CUDA on Tegra X1.
They provide a lot of drivers for CUDA and the DevKit boards, namely the Jetson TK1 and Jetson TX1. And some of the users also reported that the Shield TV has a lot in common with the TX1 boards.