The processing of USB receive transfers is common to both sides of a MCTP over USB transport. In order to support a future gadget driver, move the current host-side driver into a new common file, mctp-usblib. This currently handles the submit-complete-packetise process of the receive path of the USB transport. We'll add transmit handling in an upcoming change. Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au> Link: https://patch.msgid.link/20260724-dev-mctp-usb-1-1-v5-3-e66bbba0dbdc@codeconstruct.com.au Signed-off-by: Jakub Kicinski <kuba@kernel.org>