which CSI-2 MIPI cameras are supported?
TK1 is sold to public, ie me... public has no means to "design custom hardware & firmware & software for any specific CSI MIPI camera"
there is an expectation that one or more CSI cameras will be available.
see Raspberry Pi.
I agree that ideally a built commercial CSI camera board should be tested on Jetson TK1 and documented, but unfortunately NVIDIA has not done this and might not do it for many months or years since big customers won't want to use the same specific CSI camera board, and makers will be happy enough to use a cheap USB webcam, so NVIDIA hasn't made it a priority.
PS: Raspberry Pi did release a CSI camera board after the RPi became hugely popular, but Raspberry Pi is also about 100x more popular than any other embedded ARM board, so they have more reason to work on things like this, whereas Jetson TK1 is still very new & unknown so NVIDIA hasn't put many resources into add-on devices as yet. Hopefully this will change in the next 1 or 2 years, particularly for CSI camera & Arduino support!