When it comes to the real-time "RT" patches carried outside of the Linux kernel, a number of them pertain to adjustments around the Intel i915 kernel DRM graphics driver. The mainline Linux kernel and its RT support depend upon not building "PREEMPT_RT" for the i915 driver support while patches have been worked on recently for making this Intel kernel graphics driver code play nicely with real-time Linux...
Source: Phoronix — read the full report at the original publisher.