It os definitely more open than most, thanks! I'm pretty sure it still has the masked boot rom before getting to the open bits. While the tpl and ddr are still blobs and might harbor naughtiness, people have at least figured out how to edit the blobs https://github.com/hbiyik/rkddr
U-boot for Rockchip builds it's own TPL. I'm using it right now. It can also use Rockchip's TPL, but that's optional, not the default. DDR training code is here:
