Lucas Stach published the initial six patches to the dri-devel mailing list on Tuesday. His message reads, "This is the first set of patches to make Nouveau work on Tegra. Those are only the obvious correctness fixes, a lot of optimization work remains to be done, but at least it's enough to get accel working and let the machine survive a piglit run."
This Nouveau work is rather interesting given that already there's a NVIDIA Tegra DRM driver that's separate from Nouveau and provides DRM/KMS support for NVIDIA's ARM SoCs. This separate project has limited backing from NVIDIA but doesn't cover any 3D acceleration support. In the past there was some out-of-tree Nouveau Tegra work talked about at FOSDEM and other occasions but never received much public attention and was never merged.
Recently, NVIDIA has decided to start licensing its Kepler technology for possible SoC integration. This will be interesting to watch in the coming months and to see how the Nouveau support expands for ARM/Tegra hardware. At the moment this is Nouveau DRM work and no user-space / Mesa (Gallium3D) patches were published on Tuesday.
Update: The developers have now clarified this support is for allowing NVIDIA GPUs connected to a Tegra SoC via PCI Express to work with Nouveau but not the NVIDIA Tegra graphics core itself.