love.joystick.loadGamepadMappings
Loads a gamepad mappings string or file created with love.joystick.saveGamepadMappings.

It also recognizes any SDL gamecontroller mapping string, such as those created with Steam's Big Picture controller configure interface, or this nice database. If a new mapping is loaded for an already known controller GUID, the later version will overwrite the one currently loaded.
love.joystick.loadGamepadMappings( filename )
filename string The filename to load the mappings string from.
love.joystick.loadGamepadMappings( mappings )
mappings string The mappings string to load.