of: Create unlocked version of for_each_child_of_node()

When iterating over nodes, sometimes it needs to be done when the DT
lock is already held. This patch makes an unlocked version of the
for_each_child_of_node() macro.
Signed-off-by: Grant Likely <grant.likely@linaro.org>

drivers/of/base.c

@@ -695,6 +695,22 @@ struct device_node *of_get_next_parent(struct device_node *node)
 }
 EXPORT_SYMBOL(of_get_next_parent);
 
+static struct device_node *__of_get_next_child(const struct device_node *node,
+						struct device_node *prev)
+{
+	struct device_node *next;
+
+	next = prev ? prev->sibling : node->child;
+	for (; next; next = next->sibling)
+		if (of_node_get(next))
+			break;
+	of_node_put(prev);
+	return next;
+}
+#define __for_each_child_of_node(parent, child) \
+	for (child = __of_get_next_child(parent, NULL); child != NULL; \
+	     child = __of_get_next_child(parent, child))
+
 /**
  *	of_get_next_child - Iterate a node childs
  *	@node:	parent node
@@ -710,11 +726,7 @@ struct device_node *of_get_next_child(const struct device_node *node,
 	unsigned long flags;
 
 	raw_spin_lock_irqsave(&devtree_lock, flags);
-	next = prev ? prev->sibling : node->child;
-	for (; next; next = next->sibling)
-		if (of_node_get(next))
-			break;
-	of_node_put(prev);
+	next = __of_get_next_child(node, prev);
 	raw_spin_unlock_irqrestore(&devtree_lock, flags);
 	return next;
 }