hi,
i've 2 usb serial
after one change eeprom serial ( 0001 to 1740 )
i put in /etc/udev/rules.d/99.persistantusb.rules
SUBSYSTEM=="tty", ATTRS{idVendor}=="10c4", ATTRS{idProduct}=="ea60", ATTRS{serial}=="0001", SYMLINK+="ttyUSB0"
SUBSYSTEM=="tty", ATTRS{idVendor}=="10c4", ATTRS{idProduct}=="ea60", ATTRS{serial}=="1740", SYMLINK+="ttyUSB1"
but no good ,always :
serial 0001 = ttyUSB1
and serial 1740 = ttyUSB0