dt-bindings: mtd: fixed-partitions: Add alignment properties

Add three properties for controlling alignment of partitions, aka
'entries' in fixed-partition.

For now there is no explicit mention of hierarchy, so a 'section' is
just the 'fixed-partitions' node.

These new properties are inputs to the Binman packaging process, but are
also needed if the firmware is repacked, to ensure that alignment
constraints are not violated. Therefore they are provided as part of
the schema.
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20240412153249.100787-1-sjg@chromium.org

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

@@ -57,6 +57,57 @@ properties:
       user space from
     type: boolean
 
+  align:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 2
+    maximum: 0x80000000
+    multipleOf: 2
+    description:
+      This sets the alignment of the entry in bytes.
+
+      The entry offset is adjusted so that the entry starts on an aligned
+      boundary within the containing section or image. For example ‘align =
+      <16>’ means that the entry will start on a 16-byte boundary. This may
+      mean that padding is added before the entry. The padding is part of
+      the containing section but is not included in the entry, meaning that
+      an empty space may be created before the entry starts. Alignment
+      must be a power of 2. If ‘align’ is not provided, no alignment is
+      performed.
+
+  align-size:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 2
+    maximum: 0x80000000
+    multipleOf: 2
+    description:
+      This sets the alignment of the entry size in bytes. It must be a power
+      of 2.
+
+      For example, to ensure that the size of an entry is a multiple of 64
+      bytes, set this to 64. While this does not affect the content of the
+      entry itself (the padding is performed only when its parent section is
+      assembled), the end result is that the entry ends with the padding
+      bytes, so may grow. If ‘align-size’ is not provided, no alignment is
+      performed.
+
+  align-end:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 2
+    maximum: 0x80000000
+    multipleOf: 2
+    description:
+      This sets the alignment (in bytes) of the end of an entry with respect
+      to the containing section. It must be a power of 2.
+
+      Some entries require that they end on an alignment boundary,
+      regardless of where they start. This does not move the start of the
+      entry, so the content of the entry will still start at the beginning.
+      But there may be padding at the end. While this does not affect the
+      content of the entry itself (the padding is performed only when its
+      parent section is assembled), the end result is that the entry ends
+      with the padding bytes, so may grow. If ‘align-end’ is not provided,
+      no alignment is performed.
+
 if:
   not:
     required: [ reg ]