joystick_port_3
The option documentation is properly formatted yet
Example: LOGITECH CORDLESS RUMBLEPAD 2 USB
Emulated parallel port joystick 2. A few games support parallel port joysticks (to support a total of four connected joysticks).
Source: https://github.com/FrodeSolheim/fs-uae/blob/master/docs/options/joystick_port_3