I believe that is intended to setup a special char device for doing 'extra' paravirtualization stuff. It's a communication path for doing copy-n-paste buffers and other things. The target_type=virtio ...

The device shown in Figure 17-1 is an RS-232–to–TTL converter board, designed to allow a PC with a serial (RS-232) port to communicate with a device that has a console (TTL) port. External converters ...

For years I have been wondering when Cisco would activate the USB ports on their devices. I have been hoping for all kinds of USB functionality to routers, switches, firewalls but Cisco has been slow ...