The Microsoft Surface 3 has an Intel Atom Z8700 processor in it. This SoC contains an ISP which handles input from the device's two cameras. This ISP has no driver available currently. The ISP shows up as a PCI device.
It might be possible to build a driver based on the atomisp driver written for an older Atom platform (here: https://kernel.googlesource.com/pub/scm/linux/kernel/git/kas/3.0-mid/+/HEAD/drivers/media/video/atomisp) and Intel's datasheets.
Neither of the camera sensors in the tablet have drivers either, so it might be necessary to write at least one of those drivers first to test anything. The sensors are an Aptina AR0330 and an OmniVision OV8835.
Downgrade the importance since the cameras are not so critical for running Linux.
*** This bug has been marked as a duplicate of bug 109821 ***