+sd.add_item( ... ): Add an item to the service discovery.
+ The item object has the same members as the one in playlist.add().
+ Returns the input item.
+sd.add_node( ... ): Add a node to the service discovery.
+ The node object has the following members:
+ .title: the node's name
+ .arturl: the node's ArtURL (OPTIONAL)
+
+n = vlc.sd.add_node( {title="Node"} )
+n:add_subitem( ... ): Same as sd.add_item(), but as a subitem of n.
+n:add_node( ... ): Same as sd.add_node(), but as a subnode of n.