diff --git a/chips/lowrisc/Cargo.toml b/chips/lowrisc/Cargo.toml
index 8822d2a0f1..fae16af105 100644
--- a/chips/lowrisc/Cargo.toml
+++ b/chips/lowrisc/Cargo.toml
@@ -11,3 +11,7 @@ edition.workspace = true
 [dependencies]
 rv32i = { path = "../../arch/rv32i" }
 kernel = { path = "../../kernel" }
+
+[lints.rust]
+# These are unused and unsupported
+unexpected_cfgs = { level = "warn", check-cfg = ['cfg(aon_wkup_timer)'] }
diff --git a/doc/CodeReview.md b/doc/CodeReview.md
index e0284f5387..baf49d513f 100644
--- a/doc/CodeReview.md
+++ b/doc/CodeReview.md
@@ -344,6 +344,15 @@ Generally, this means `cfg` directives should be an explicit list of chips or'd
 together. Rarely, if ever, is a `cfg(not ...)` the correct approach for anything
 outside of unit tests.
 
+Rust `cfg` features can also be used to disable code that isn't used in upstream
+Tock but might be used in private or public forks. Rust custom configs can also
+be used, but generally require changes to the lint configuration. See
+https://doc.rust-lang.org/nightly/rustc/check-cfg/cargo-specifics.html#check-cfg-in-lintsrust-table
+for more details on getting the Rust lints to pass.
+
+It would be better to use Cargo feature flags then `cfg`s and avoinding compile
+time configuration at all would be best.
+
 #### Boards
 
 Changes to boards are generally left to the maintainer or original contributor