OS X supports HID or human interface device. HID uses the same definitioned used in the standard USB HID specification (although you don't need to have a USB device to make an HID device, it could be ADB or whatever). HID is pretty low level and defines all kinds of input devices like tablets, joysticks, gamepads, whatever.
Most USB input devices ought to define themselves in the HID spec so no driver is really necessary. However if you want to configure a controller for a game which doesn't interface with HID we'll need a 3rd party utility which does this mapping.
I plan to write an ADB driver for my thrustmaster joystick once Griffin Tech releases an iMate driver. It will behave just like a USB joystick.