You can name this topic as a youtube sub exchange to be more specific.
But if you want to develop your last long channel, I recommend you try to make more related video and then show your videos to every one so they will watch it and then watch another video of your channel if they interesting. Because when you just ask people subcribe your channel, they will do it but after that your video will not be watch naturally.
I know about making good content, each one of my videos generally get 20K views or more over time, but people are more apt to hit subscribe once you hit 1,000 subscribers.
