diff --git a/documentation/content/en/books/porters-handbook/special/_index.adoc b/documentation/content/en/books/porters-handbook/special/_index.adoc
--- a/documentation/content/en/books/porters-handbook/special/_index.adoc
+++ b/documentation/content/en/books/porters-handbook/special/_index.adoc
@@ -505,6 +505,9 @@
 |`CARGO_CRATES`
 |
 |List of crates the port depends on. Each entry needs to have a format like `cratename-semver` for example, `libc-0.2.40`. Port maintainers can generate this list from [.filename]#Cargo.lock# using `make cargo-crates`. Manually bumping crate versions is possible but be mindful of transitive dependencies.
+If the list generated by `make cargo-crates` is big, it might be convenient to place it inside a `Makefile.crates` file in the top-level port directory.
+If present, the ports framework sources that file automatically.
+This helps keeping the main port Makefile withing a reasonable size.
 
 |`CARGO_FEATURES`
 |