In case there is an additional "partitions" subnode between the device
itself and its partitions like /soc/spi@?/mram@?/partitions/partition@?
also try the parent of the parent before giving up finding the device
node.

See kernel docs for reference:
  Documentation/devicetree/bindings/mtd/partition.txt

Signed-off-by: Bastian Stender <bst@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>