Document the SDK support policy

firebase.json

@@ -388,6 +388,7 @@
       { "source": "/to/publish-from-github", "destination": "/tools/pub/automated-publishing#publishing-packages-using-github-actions", "type": 301 },
       { "source": "/to/publish-with-service-account", "destination": "/tools/pub/automated-publishing#publishing-from-google-cloud-build", "type": 301 },
       { "source": "/to/pubspec-overrides", "destination": "/tools/pub/dependencies#pubspec-overrides", "type": 301 },
+      { "source": "/to/sdk-support-policy", "destination": "/tools/sdk#support-policy", "type": 301 },
       { "source": "/to/sdk-constraint", "destination": "/tools/pub/pubspec#sdk-constraints", "type": 301 },
       { "source": "/to/sdk-version-pinning", "destination": "https://github.com/dart-lang/sdk/blob/main/docs/Flutter-Pinned-Packages.md", "type": 301 },
       { "source": "/to/web-debug-extension", "destination": "https://chromewebstore.google.com/detail/dart-debug-extension/eljbmlghnomdjgdjmbdekegdkbabckhm", "type": 301 },

src/content/get-dart/index.md

@@ -11,6 +11,10 @@ This page describes how to download the Dart SDK.
 The Dart SDK includes the libraries and command-line tools that
 you need to develop Dart command-line, server, and web apps.
 
+The Dart team supports only the latest stable release of the SDK.
+For full details on the SDK release lifecycle and supported versions,
+check out the [SDK support policy](/tools/sdk#support-policy).
+
 To learn more about the Dart SDK, consult the [Dart SDK overview](/tools/sdk).
 
 :::tip

src/content/tools/sdk.md

@@ -42,6 +42,32 @@ The Dart SDK includes two directories:
 
 To learn more about the SDK, check out its [README file][readme].
 
+## Support policy
+
+The Dart team supports only the latest, stable version of the Dart SDK.
+When a new major or minor version is released,
+older versions are no longer supported.
+For example, if `3.7.x` is the latest release,
+it is supported until `3.8.0` or `4.0.0` is released,
+whichever comes first.
+
+The Dart team provides fixes to critical issues and security problems as needed
+through patch releases but only for the currently supported version.
+For example, if `3.7.0` is the latest stable release,
+a fix to a vulnerability might be issued in a `3.7.1` patch release.
+
+On average, the Dart team ships a new stable release every 3 months.
+Patch releases to the currently supported version are shipped as needed.
+
+This policy helps ensure Dart developers have access to
+a stable and reliable platform that continues to
+evolve with new features and improvements.
+
+{% comment %}
+TODO(parlough): Add a section discussing the breaking change policy
+and link out to the breaking change index.
+{% endcomment %}
+
 ## Filing bugs and feature requests
 
 To see existing issues or create a new one,