* gnu/services/networking.scm (usb-modeswitch-service-type): New variable.
(usb-modeswitch-configuration): New variable.
(usb-modeswitch-sh): New procedure.
(usb-modeswitch-configuration->udev-rules): New procedure.
* doc/guix.texi (Networking Services): Document it.
Signed-off-by: Ludovic Courtès <ludo@gnu.org>