of: add of_parse_phandle() helper for parsing phandle properties

of_parse_phandle() is a helper function to read and parse a phandle
property and return a pointer to the resulting device_node.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Andy Fleming <afleming@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/of/base.c

@@ -494,6 +494,30 @@ int of_modalias_node(struct device_node *node, char *modalias, int len)
 }
 EXPORT_SYMBOL_GPL(of_modalias_node);
 
+/**
+ * of_parse_phandle - Resolve a phandle property to a device_node pointer
+ * @np: Pointer to device node holding phandle property
+ * @phandle_name: Name of property holding a phandle value
+ * @index: For properties holding a table of phandles, this is the index into
+ *         the table
+ *
+ * Returns the device_node pointer with refcount incremented.  Use
+ * of_node_put() on it when done.
+ */
+struct device_node *
+of_parse_phandle(struct device_node *np, const char *phandle_name, int index)
+{
+	const phandle *phandle;
+	int size;
+
+	phandle = of_get_property(np, phandle_name, &size);
+	if ((!phandle) || (size < sizeof(*phandle) * (index + 1)))
+		return NULL;
+
+	return of_find_node_by_phandle(phandle[index]);
+}
+EXPORT_SYMBOL(of_parse_phandle);
+
 /**
  * of_parse_phandles_with_args - Find a node pointed by phandle in a list
  * @np:		pointer to a device tree node containing a list