software node: Implement get_named_child_node fwnode callback

This makes it possible to support drivers that use
fwnode_get_named_child_node() and device_get_named_child_node()
functions.

The node name is for now taken from a device property named
"name". That mimics the old style of naming of the nodes in
devicetree (though with modern flattened DT, the name is
matched against the actual node-name, it used to be done
with a property "name"). In Open Firmware DT the "name"
property is also still being used.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/swnode.c

@@ -499,6 +499,28 @@ software_node_get_next_child(const struct fwnode_handle *fwnode,
 	return &c->fwnode;
 }
 
+static struct fwnode_handle *
+software_node_get_named_child_node(const struct fwnode_handle *fwnode,
+				   const char *childname)
+{
+	struct software_node *swnode = to_software_node(fwnode);
+	const struct property_entry *prop;
+	struct software_node *child;
+
+	if (!swnode || list_empty(&swnode->children))
+		return NULL;
+
+	list_for_each_entry(child, &swnode->children, entry) {
+		prop = property_entry_get(child->properties, "name");
+		if (!prop)
+			continue;
+		if (!strcmp(childname, prop->value.str)) {
+			kobject_get(&child->kobj);
+			return &child->fwnode;
+		}
+	}
+	return NULL;
+}
 
 static const struct fwnode_operations software_node_ops = {
 	.get = software_node_get,
@@ -508,6 +530,7 @@ static const struct fwnode_operations software_node_ops = {
 	.property_read_string_array = software_node_read_string_array,
 	.get_parent = software_node_get_parent,
 	.get_next_child_node = software_node_get_next_child,
+	.get_named_child_node = software_node_get_named_child_node,
 };
 
 /* -------------------------------------------------------------------------- */