P.S. Please add a license for your code.
[1] https://tree-sitter.github.io/
[2] https://github.com/rizinorg/rizin/tree/dev/librz/type/parser
TL;DR: you declare a variable in C _in exactly the same way you would use it:_ if you know how to use a variable, then you know how to read and write a declaration for it.
https://eigenstate.org/notes/c-decl https://news.ycombinator.com/item?id=12775966