Using USB with a serial connecting camera

Using Suse 9.3 and 10.1. I have two serial ports. Only one can be used and is connected with my modem. The other serial port is not working. I have recently bought an USB serial cable and now want to use that cable to make a connection with my camera. In Digikam my camera is included but there is no choice of USB, Serial it is. I could insert a camera port path. The camera mount path is grayed out. Is there a possibility to tell Digikam the the serial port path is "whatever" and symlink that port to the USB port from the cable. How do I find out the path to mount the USB?