I don't think there is a specifically IR uart driver in the kernel - there is IR and there is serial, but I don't know that there's a valid connection between the two. It's probably not TOO difficult to get it to treat an IR port as a serial device.
Also, if it's just a serial connection to the device, it's not a kernel driver, but a user-space program that handles the communication with the device - the uart will be transparent in that case. The kernel will handle the PC side of the serial driver, but any communication that goes on between the serial port and the IR device will have to be interpreted by a separate program, which, again, wouldn't be a kernel issue - that would be user-space.
If you have more info, I could probably help a lot more - your question was very general.