dt-bindings: mtd: partitions: support label/name only partition

Document new partition nodes that declare only the label/name instead
of the reg used to provide an OF node for partition registred at runtime
by parsers. This is required for nvmem system to declare and detect
nvmem-cells.

With these special partitions, the reg / offset is not required and a
'partition-' prefix is needed.
The node name with the 'partition-' prefix stripped, is used to match
the partition allocated by the parser at runtime and the parser will
provide reg and offset of the mtd.
If the partition to match contains invalid char for a node name, the
label binding can be used to declare the partition name.

NVMEM will use the data from the parser and provide the NVMEM cells
declared in the DTS, "connecting" the dynamic partition with a
static declaration of cells in them.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220622010628.30414-2-ansuelsmth@gmail.com

Documentation/devicetree/bindings/mtd/partitions/partition.yaml

@@ -11,6 +11,17 @@ description: |
   relative offset and size specified. Depending on partition function extra
   properties can be used.
 
+  A partition may be dynamically allocated by a specific parser at runtime.
+  In this specific case, a specific suffix is required to the node name.
+  Everything after 'partition-' will be used as the partition name to compare
+  with the one dynamically allocated by the specific parser.
+  If the partition contains invalid char a label can be provided that will
+  be used instead of the node name to make the comparison.
+  This is used to assign an OF node to the dynamiccally allocated partition
+  so that subsystem like NVMEM can provide an OF node and declare NVMEM cells.
+  The OF node will be assigned only if the partition label declared match the
+  one assigned by the parser at runtime.
+
 maintainers:
   - Rafał Miłecki <rafal@milecki.pl>
 
@@ -41,7 +52,12 @@ properties:
       immune to paired-pages corruptions
     type: boolean
 
-required:
-  - reg
+if:
+  not:
+    required: [ reg ]
+then:
+  properties:
+    $nodename:
+      pattern: '^partition-.*$'
 
 additionalProperties: true