PMOS reverse polarized - 12v light
That is not a good circuit.

In real life voltage sources vary from their nominal values.  For example in a car the 12v battery can be anywhere between 9v and 16v.

If V3 is more than about 0.7v more than V1 and SW2 is activated you could get damaging current flowing through the body diode of the MOSFET.

Similarly is V1 is higher than V3 and both SW1 and SW2 are closed you could get damaging current flow through the MOSFET into V3

One way to modify the circuit if you want the lamp to operate if SW1 or SW2 is closed is to add two diodes feeding the lamp: one from the MOSFET and one from SW2.

That way whichever supply is the higher will supply the power to the lamp.