Actually, USB subsystem has no role.

Behavior

Micro USB device connector, is routed to Carberry microcontroller, and acts as CDC Emulation terminal.
In fact, if you connect Carberry USB to a PC (Windows or Linux hosted) you can talk with Carberry, using the same syntax used for Raspberry Pi UART.

Drivers

Depending by OS used, you may need or not to install specific USB drivers.

Linux

With Linux host, you don't need any drivers to talk with Carberry via USB.
Just plug Carberry into USB host, and look at the new device.

ls /dev

And you have to see something like /dev/ttyUSB1

Windows

With Windows host, you have to install this specific driver to talk with Carberry via USB.
Download USB drivers, plug Carberry USB connector into host PC, and install drivers when requested\\. In Device Manager in Control Panel, you will have a new COMxx port installed.