On Monday, August 22, 2016 11:23:26 PM CEST H. Nikolaus Schaller wrote:

I see what you mean, but kernel divides between directly connected UART and USB-connected UART.

drivers/usb/serial/ vs. drivers/tty/serial/

That distinction purely exists for historic reasons. I'd argue that the
former should actually go into drivers/tty/usb or similar. A long time
ago, we commonly sorted device drivers by how they were attached to
the system (as drivers/usb/serial/ and drivers/usb/storage still do),
but almost everything is now sorted according to how it is used instead.

	Arnd