dt-bindings: net: Add network-class schema for mac-address properties

dt-bindings: net: Add network-class schema for mac-address properties

The ethernet-controller schema specifies "mac-address" and
"local-mac-address" but other network devices such as wireless network
adapters use mac addresses as well.
The Devicetree Specification, Release v0.3 specifies in section 4.3.1
a generic "Network Class Binding" with "address-bits", "mac-address",
"local-mac-address" and "max-frame-size". This schema specifies the
"address-bits" property and moves the remaining properties over from
the ethernet-controller.yaml schema.

The "max-frame-size" property is used to describe the maximal payload
size despite its name. Keep the description from ethernet-controller
specifying this property as MTU. The contradictory description in the
Devicetree Specification is ignored.

Signed-off-by: Janne Grunau <j@jannau.net>
Signed-off-by: David Heidelberg <david@ixit.cz>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20250324-dt-bindings-network-class-v5-1-f5c3fe00e8f0@ixit.cz
Signed-off-by: Johannes Berg <johannes.berg@intel.com>