I've merged 3.8.13.26-rt31 with the odroid-3.8.y branch, and I got a kernel
that has reasonable realtime performance on my Odroid U3. I've put the tree
(including my config, as arch/arm/configs/odroidu_defconfig)
on github.
The U3 isn't without annoyances and the idea
of LinuxCNC on ARM isn't free from worries, but
I now have a platform dedicated to devloping linuxcnc uspace that draws only
2W when idle, and can build LinuxCNC from clean in about 4 minutes. Not bad!