ofnode: add ofnode_by_prop_value()

Adds ofnode_by_prop_value() to search for nodes with a given property
and value, an ofnode version of fdt_node_offset_by_prop_value().

Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/include/dm/of_access.h b/include/dm/of_access.h
index dd1abb8..5ed1a0c 100644
--- a/include/dm/of_access.h
+++ b/include/dm/of_access.h
@@ -194,6 +194,22 @@
 				const char *type, const char *compatible);
 
 /**
+ * of_find_node_by_prop_value() - find a node with a given property value
+ *
+ * Find a node based on a property value.
+ * @from: Node to start searching from or NULL. the node you pass will not be
+ *	searched, only the next one will; typically, you pass what the previous
+ *	call returned.
+ * @propname: property name to check
+ * @propval: property value to search for
+ * @proplen: length of the value in propval
+ * @return node pointer or NULL if not found
+ */
+struct device_node *of_find_node_by_prop_value(struct device_node *from,
+					       const char *propname,
+					       const void *propval,
+					       int proplen);
+/**
  * of_find_node_by_phandle() - Find a node given a phandle
  *
  * @handle:	phandle of the node to find