Bus 003 Device 002: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port
[54027.595634] USB Serial support registered for pl2303
[54027.595855] pl2303 3-1:1.0: pl2303 converter detected
[54027.607264] usb 3-1: pl2303 converter now attached to ttyUSB0
So I analyzed it and found that it seemed like a 3.3V serial adaptor, so I had to start using it to access routers, mobiles, ... having also a broken Fonera power supply around (one of this typical Fonera problems where the power supply outputs the correct voltage but not enough intensity) I thought... if I put all this together I'll have a USB cable capable of powering La Fonera and also accessing it's serial port all in one and using just one USB slot.
And so... here is what I think is the definitive Fonera cable: