Here's a reel composed by Josephne Keegan. I can't tell you much about the title though I know that a gate is like a door with the outside on its inside and outside; a Mullagh (or mullach) is a hilltop and so lots of hilly places are named after this feature:http://www.teanglann.ie/en/fgb/mullach. 

Here are some dots: https://thesession.org/tunes/2243