edit parsing

Author: pierwill

src/overview.md

@@ -137,6 +137,17 @@ diagnostic infrastructure in `rustc`. Instead it provides diagnostics as plain
 data which are emitted in `rustc_parse::lexer::mod` as real diagnostics.
 The lexer preserves full fidelity information for both IDEs and proc macros.
 
+The *parser* [translates the token stream from the lexer into an Abstract Syntax
+Tree (AST)][parser]. It uses a recursive descent (top-down) approach to syntax
+analysis. The crate entry points for the parser are the
+[`Parser::parse_crate_mod()`][parse_crate_mod] and [`Parser::parse_mod()`][parse_mod]
+methods found in [`rustc_parse::parser::Parser`]. The external module parsing
+entry point is [`rustc_expand::module::parse_external_mod`][parse_external_mod].
+And the macro parser entry point is [`Parser::parse_nonterminal()`][parse_nonterminal].
+
+Parsing is performed with a set of `Parser` utility methods including `bump`,
+`check`, `eat`, `expect`, `look_ahead`.
+
 
 [String interning]: https://en.wikipedia.org/wiki/String_interning
 [`rustc_lexer`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lexer/index.html