With this libav commit is the few hundred lines of code needed to support accelerated HEVC decoding with VA-API.
Back in 2014 is when VA-API itself landed HEVC decode while last year also brought HEVC encode support. VA-API decode was also implemented in the Gallium3D state tracker and then for Intel's VA-API driver is supported with Skylake and newer though not until Kabylake is there full 10-bit H.265 support.
This comes after Libav recently implemented VA-API accelerated VP8 decoding (finally!) as well as VA-API accelerated de-interlacing.