Perhaps not what you want, but you can connect to Raspberry serial via USB2TTY:
https://www.raspberrypi.org/forums/view ... 3&t=156541
You can then use minicom or screen tools to login to Raspberry and "telnet" on Raspberry to connect to target.
I learned that it is important to get 5V from USB, but use USB2TTY with 3.3V setting in addtion for serial:
That was first attempt, not good because of 5V to serial: