The pull request was sent in by AMD's Christian König and tries to add support for their newly-announced Mullins APUs. This pull comes shortly after AMD announced open-source Mullins/Beema APU support, one day after the APUs were announced. Support for the new AMD graphics hardware might come in still for the Linux 3.15 kernel even though it's past the merge window since the GPU is based upon AMD's Kabini and mostly deals with adding new PCI IDs and enums to the kernel driver. There's also the libdrm and Mesa RadeonSI Gallium3D updates needed in user-space for complete support.
Other fixes part of this latest kernel pull include Dynamic Power Management (DPM) updates for Kabini hardware, PLL limit changes, and other fixes.
More details on this latest Radeon Linux 3.15 pull can be found via the latest pull request. Yesterday I delivered some early Linux 3.15 Radeon benchmarks for those interested.