dt-bindings: net: Add switch ports and interrupts to RTL9300

Add bindings for the ethernet-switch and interrupt properties for the
RTL9300.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20250218195216.1034220-3-chris.packham@alliedtelesis.co.nz


Signed-off-by: Jakub Kicinski <kuba@kernel.org>