docs(ref): Set Rust version support expectations

src/doc/src/reference/rust-version.md

@@ -15,8 +15,6 @@ identifiers such as -nightly will be ignored while checking the Rust version.
 
 To find the minimum `rust-version` compatible with your project, you can use third-party tools like [`cargo-msrv`](https://crates.io/crates/cargo-msrv).
 
-When used on packages that get published, we recommend [verifying the `rust-version`](../guide/continuous-integration.md#verifying-rust-version).
-
 > **MSRV:** Respected as of 1.56
 
 ## Uses
@@ -36,3 +34,31 @@ Other tools may also take advantage of it, like `cargo clippy`'s
 [`incompatible_msrv` lint](https://rust-lang.github.io/rust-clippy/master/index.html#/incompatible_msrv).
 
 > **Note:** The `rust-version` may be ignored using the `--ignore-rust-version` option.
+
+## Support Expectations
+
+These are general expectations; some packages may document when they do not follow these.
+
+**Complete:**
+
+All functionality, including binaries and API, are available on the supported Rust versions under every [feature](features.md).
+
+**Verified:**
+
+A package's functionality is verified on its supported Rust versions, including automated testing.
+See also our
+[Rust version CI guide](../guide/continuous-integration.md#verifying-rust-version).
+
+**Patchable:**
+
+For license that allow it,
+users can fork your package, modify it, and [override their local dependency](overriding-dependencies.md) to use their fork.
+Cargo may load the entire workspace for a patched dependency which should work on the supported Rust versions.
+
+**Dependency Support:**
+
+In support of the above,
+it is expected that each dependency's version-requirement supports at least one version compatible with your `rust-version`.
+However,
+it is **not** expected that the dependency specification excludes versions incompatible with your `rust-version`.
+In fact, supporting both allows you to balance the needs of users that support older Rust versions with those that don't.