- Re-create Godot's basic types in your new language: These are types such as Vector3, int, float, String, etc. Many of these are usually provided already.
- Create a module: A C++ module that creates binding code needs to be done (creating modules in C++ is well documented). The entire exposed Godot API can be accessed via the static functions in ObjectTypeDB.
- Generate binding code in your new language that accesses the exposed functions in the MethodBind class (there is one for each exposed method).
- Create a ScriptLanguage class and supply the neccesary methods exposed for debugging, profiling, etc. You can supply symbols, code completion helpers, etc. if this language is meant to be edited inside Godot.