Here sorry I missed earlier but this will take care of the USB to serial modules for all linux compatible devices on Maemo:

http://www.electronicproductonline.com/catalog/supportFiles/usbSerial-N810_0.1_armel.deb

I've used this before and serial devices always show up properly. I think ftdi (?) chips are the most common for microcontrollers like arduino, the pl2303's tend to be more for the stand alone USB-serial adapters... but that's just been my experience, don't know for sure!