Reference for context-free grammar for Martin-Löf type theory
Generally, there will be one context-free grammar for both types and terms, and judgements will be used to identify those expressions which are types and which expressions are terms of a particular type.
This has been written down many, many times. For a pretty typical example, you could look at Abel, Coquand and Dybjer's LICS 2007 paper, Normalization by Evaluation for Martin-Löf Type Theory with Typed Equality Judgements.