I used to linux USB port naming, aka /dev/ttyUSBxx and currently trying to write some test software to read/write raw data to USB ports on iMac, but i find it hard to detect to which port my usb hardware is connected. I have tried up to a using /dev/ttys"x" but no luck.
In the system information i see the hardware attached at Location ID: 0xfa120000 / 6 maybe this can help somehow?
OS X doesn't create a /dev entry for raw access to USB devices, and there's no way to access them as TTY devices.
Partly this is a different in philosophy between Linux and BSD, partly it's a difference in driver-writing technology, and partly it's a matter of already having a well-defined hierarchy (the IOKit Registry) that would have to be mapped to the /dev hierarchy in some complicated way.
At any rate, if you want to learn how you should access USB devices on a Mac, start with QA1370. If you're looking to do a quick port of some linux code without actually learning IOKit/IOUSB, it's probably going to be impossible. If you're looking for something else, you'll need to give more info about what you're trying to do.