of: base: Add of_get_available_child_by_name()

There are lot of drivers using of_get_child_by_name() followed by
of_device_is_available() to find the available child node by name for a
given parent. Provide a helper for these users to simplify the code.

Suggested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/of/base.c

@@ -824,6 +824,33 @@ struct device_node *of_get_child_by_name(const struct device_node *node,
 }
 EXPORT_SYMBOL(of_get_child_by_name);
 
+/**
+ * of_get_available_child_by_name - Find the available child node by name for a given parent
+ * @node:	parent node
+ * @name:	child name to look for.
+ *
+ * This function looks for child node for given matching name and checks the
+ * device's availability for use.
+ *
+ * Return: A node pointer if found, with refcount incremented, use
+ * of_node_put() on it when done.
+ * Returns NULL if node is not found.
+ */
+struct device_node *of_get_available_child_by_name(const struct device_node *node,
+						   const char *name)
+{
+	struct device_node *child;
+
+	child = of_get_child_by_name(node, name);
+	if (child && !of_device_is_available(child)) {
+		of_node_put(child);
+		return NULL;
+	}
+
+	return child;
+}
+EXPORT_SYMBOL(of_get_available_child_by_name);
+
 struct device_node *__of_find_node_by_path(const struct device_node *parent,
 						const char *path)
 {

include/linux/of.h

@@ -301,6 +301,8 @@ extern struct device_node *of_get_compatible_child(const struct device_node *par
 					const char *compatible);
 extern struct device_node *of_get_child_by_name(const struct device_node *node,
 					const char *name);
+extern struct device_node *of_get_available_child_by_name(const struct device_node *node,
+							  const char *name);
 
 /* cache lookup */
 extern struct device_node *of_find_next_cache_node(const struct device_node *);
@@ -578,6 +580,13 @@ static inline struct device_node *of_get_child_by_name(
 	return NULL;
 }
 
+static inline struct device_node *of_get_available_child_by_name(
+					const struct device_node *node,
+					const char *name)
+{
+	return NULL;
+}
+
 static inline int of_device_is_compatible(const struct device_node *device,
 					  const char *name)
 {