Automatically create a fixed symbolic link when a device is attached

My laptop had two USB devices that was mapped everytime to differents /dev/ttyUSB paths.
For example sometime:

[9.019817] usb 2-1.4: Qualcomm USB modem converter now attached to ttyUSB0
[9.053636] usb 2-1.6: pl2303 converter now attached to ttyUSB1

or sometime so:

[9.053636] usb 2-1.6: pl2303 converter now attached to ttyUSB0
[9.019817] usb 2-1.4: Qualcomm USB modem converter now attached to ttyUSB1

The "pl2303 converter" is a USB-serial adapter that I need for some special hardware.
Because of this inconsistent mapping I needed to change quite often the settings in my software.

To solve the problem I created a symbolic device link for the USB-serial adapter, as described below:

1 step: detect the "idVendor" and "idProduct" of your hardware

$ lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 003: ID 147e:2016 Upek Biometric Touchchip/Touchstrip Fingerprint Sensor
Bus 001 Device 004: ID 0a5c:217f Broadcom Corp. Bluetooth Controller
Bus 001 Device 005: ID 17ef:1009 Lenovo 
Bus 001 Device 006: ID 17ef:480f Lenovo Integrated Webcam [R5U877]
Bus 002 Device 003: ID 05c6:9204 Qualcomm, Inc. 
Bus 002 Device 004: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port
Bus 001 Device 007: ID 046d:c018 Logitech, Inc. Optical Wheel Mouse
Bus 001 Device 008: ID 046a:0023 Cherry GmbH CyMotion Master Linux Keyboard
Bus 003 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub

In my case was the "Prolific Technology, Inc. PL2303 Serial Port". The "idVendor" is 067b while the "idProduct" is 2303

2 step: add an udev rule to create a symbolic device link everytime that the hardware is attached.
go to '/etc/udev/rules.d/' and create a file named for example '97-local.rules' with this content:

kernel=="ttyUSB*", SYSFS{idVendor}=="067b", SYSFS{idProduct}=="2303", SYMLINK="SerialUSB"

3 step: restart you system... you've done!
Give a look to your /dev directory. You shoud now see a device named /dev/SerialUSB

You can create udev rules also for other purposes, for example run a script when a new hardware is detected.