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: NGrant Likely <grant.likely@secretlab.ca>
Acked-by: NAndy Fleming <afleming@freescale.com>
Signed-off-by: NDavid 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

include/linux/of.h

@@ -77,6 +77,9 @@ extern int of_n_size_cells(struct device_node *np);
 extern const struct of_device_id *of_match_node(
 	const struct of_device_id *matches, const struct device_node *node);
 extern int of_modalias_node(struct device_node *node, char *modalias, int len);
+extern struct device_node *of_parse_phandle(struct device_node *np,
+					    const char *phandle_name,
+					    int index);
 extern int of_parse_phandles_with_args(struct device_node *np,
 	const char *list_name, const char *cells_name, int index,
 	struct device_node **out_node, const void **out_args);