GPS setup and serial port

I have notice that different to prior versions, the system automagically detects the gps and connects it to serial 3. i prefer to have more control over it, where can i see the service that assignes a port and makes the connection.

You can find the parameters relating to GPS setup here:

Also you might be able to control which serial ports are enabled for which protocols using the serial parameters here

If you’re on Pixhawk4, this link explains the UART mapping to external plugs: