In Windows it is possible to create a virtual COM port to communicate with an USB device. However I could not find any specification how this actually works under the hood, i.e. how input to this device is converted into USB commands (control commands, I suppose) and back.

I'm asking because I have a USB device which has lots of documentation how to control it via virtual COM ports but I'd like to use it on non-Windows Systems (i.e. with libusb).

If anyone can point me to a RFC or similar, I'd be really happy: reverse-engineering the commands via USB capture would take way more time...