Polaris 12 just came to light earlier this month when some people discovered references to it in a macOS driver update. Polaris 12 is not the forthcoming high-end Vega hardware. But Polaris 12 details beyond that are rather light.
Now AMD developer Alex Deucher has published patches by AMD's Junwei Zhang that implement Polaris 12 support. Supporting Polaris 12 is just shy of 100 lines of code needed on top of the current AMDGPU DRM driver.
The series was published moments ago. Most of the ~100 lines are just for adding new "Polaris12" cases to various areas that are shared with Polaris 10/11 and then just different firmware file names. It's rather all straight-forward changes in digging through the patches with no breakthrough details, due to using all of the common Polaris 10/11 code-paths. The only new real information are the PCI IDs with there being six listed for Polaris 12: 0x6980, 0x6981, 0x6985, 0x6986, 0x6987, and 0x699F.
While writing this article, the RadeonSI Gallium3D patches for Polaris 12 were just published and again are non-exciting but basically adding the PCI IDs and the new Polaris 12 class.
Should be interesting to see what Polaris 12 is about in 2017. Given the patches aren't invasive, it's not clear yet if AMD will try getting them into Linux 4.10 or if this material will wait until Linux 4.11.