Say Y here if you have a USB device that provides normal serial
ports, or acts like a serial device, and you want to connect it to
your USB bus.

Please read Documentation/usb/usb-serial.rst for more
information on the specifics of the different devices that are
supported, and on how to use them.

To compile this driver as a module, choose M here: the
module will be called usbserial.

source code:

drivers/usb/serial/