Well known Linux game porter Ryan Gordon pushed to SDL mainline on Sunday support for using SDL2 on Mir. SDL2 already supports running on an X.Org Server and Wayland but now there's the option of using Mir, as is needed by Ubuntu Touch and then future versions of the Ubuntu desktop with 14.10 and later where it will appear by default.
This Mir video target for SDL seems to be principally designed by Brandon Schaefer at Canonical. This optional Mir SDL2 support will be found in the next SDL release and can be viewed via this SVN revision. This video back-end will allow SDL2 games to seamlessly run across X11, Wayland, and Mir platforms without needing any recompilation or changes. This is especially good for Steam-distributed games where SDL2 is already heavily relied upon as part of their run-time.
Update & Note: The Mir/Wayland support is disabled by default in SDL 2.0.2 but can be easily enabled by configuring SDL2 at build-time with either the -enable-video-wayland or --enable-video-mir switches. It's also worth pointing out that none of the Mesa/Gallium3D drivers or X.Org DDX drivers yet have mainline support for Mir/XMir. There also is not yet any mainline support in GTK, Qt, or EFL for Mir. This support is still being maintained out-of-tree and patched by Canonical for their Ubuntu packages.