In laptops there are usually embedded controllers accepting SMBus (I2C) or whatever custom protocol you might come up with.

But, as Jeroen mentioned above, it might be USB as well - in fact, it is much more probable - the laptop makers often only glue together parts without any attempt to make things simpler - there's no incentive for it, once a part supports USB and there are multi-port root hubs built into the main chipset anyway, there's no money in sparing down these things and writing a custom firmware for a nonstandard connection or whatever.

JW