Creating control rig nodes in C++?

Hey guys, I am trying to find information about control rig nodes. We have a fairly complex facial rig in maya that we are looking to move into control rig.
As of right now we are just recreating the maya nodes in control rig and its quite a chore and becoming a very large graph. It would be nice to be able to make our own nodes in C++ to be used int control rig. I have been digging around and can not find where nodes like Remap and Clamp are defined.
Are we able to create our own nodes to be used in a control rig?
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