Welcome SDL2 to the FreeBSD ports system!
A set of new SDL2 related ports has been added, which are essentially
the same as their corresponding port for SDL1.2:
A set of new USE_SDL knobs is available to enable SDL2 and its related
ports to be added as dependency to ports. Use either of
USE_SDL= sdl2 image2 mixer2 net2 ttf2
to pull in the specific sdl2_* or sdl20 port.