dt-bindings: nvmem: brcm,nvram: add #nvmem-cell-cells for MACs

Broadcom's NVRAM contains MACs for Ethernet interfaces. Those MACs are
usually base addresses that are also used for calculating other MACs.

For example if a router vendor decided to use gmac0 it most likely
programmed NVRAM of each unit with a proper "et0macaddr" value. That is
a base.

Ethernet interface is usually connected to switch port. Switch usually
includes few LAN ports and a WAN port. MAC of WAN port gets calculated
as relative address to the interface one. Offset varies depending on
device model.

Wireless MACs may also need to be calculated using relevant offsets.

To support all those scenarios let MAC NVMEM cells be referenced with an
index specifying MAC offset. Disallow additionalProperties while at it.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Message-ID: <20230611140330.154222-4-srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/nvmem/brcm,nvram.yaml

@@ -36,14 +36,29 @@ properties:
   et0macaddr:
     type: object
     description: First Ethernet interface's MAC address
+    properties:
+      "#nvmem-cell-cells":
+        description: The first argument is a MAC address offset.
+        const: 1
+    additionalProperties: false
 
   et1macaddr:
     type: object
     description: Second Ethernet interface's MAC address
+    properties:
+      "#nvmem-cell-cells":
+        description: The first argument is a MAC address offset.
+        const: 1
+    additionalProperties: false
 
   et2macaddr:
     type: object
     description: Third Ethernet interface's MAC address
+    properties:
+      "#nvmem-cell-cells":
+        description: The first argument is a MAC address offset.
+        const: 1
+    additionalProperties: false
 
 unevaluatedProperties: false