Add Brew upgrade instructions

docs/developer/release/9-update-homebrew.md

@@ -0,0 +1,18 @@
+# Update Homebrew
+
+After a stable or patch release is created, a bot will automatically create a PR in the [homebrew-grafana][] repository.
+The PR will bump the version of Agent in Agent's Brew formula.
+
+There will only be one PR for each release, and it will be for `grafana-agent-flow`.
+There is no Brew formula for `grafana-agent`. 
+
+## Steps
+
+1. Navigate to the [homebrew-grafana][] repository.
+
+2. Find the PR which bumps the Agent formula to the release that was just published. It will look like [this one][example-pr].
+
+3. Merge the PR.
+
+[homebrew-grafana]: https://github.com/grafana/homebrew-grafana
+[example-pr]: https://github.com/grafana/homebrew-grafana/pull/87

docs/developer/release/README.md

@@ -25,15 +25,15 @@ responsible for ownership of the following workflows:
 4. [Tag Release](./4-tag-release.md)
 5. [Publish Release](./6-publish-release.md)
 6. [Test Release](./7-test-release.md)
-7. [Announce Release](./9-announce-release.md)
+7. [Announce Release](./10-announce-release.md)
 
 ## Additional Release Candidate[s] Publish
 1. [Cherry Pick Commits](./2-cherry-pick-commits.md)
 2. [Update Version in Code](./3-update-version-in-code.md)
 3. [Tag Release](./4-tag-release.md)
 4. [Publish Release](./6-publish-release.md)
 5. [Test Release](./7-test-release.md)
-6. [Announce Release](./9-announce-release.md)
+6. [Announce Release](./10-announce-release.md)
 
 ## Stable Release Publish
 1. [Cherry Pick Commits](./2-cherry-pick-commits.md)
@@ -42,16 +42,18 @@ responsible for ownership of the following workflows:
 4. [Publish Release](./6-publish-release.md)
 5. [Test Release](./7-test-release.md)
 6. [Update Helm Charts](./8-update-helm-charts.md)
-7. [Announce Release](./9-announce-release.md)
-8. [Update OTEL Contrib](./10-update-otel.md)
+7. [Update Homebrew](./9-update-homebrew.md)
+8. [Announce Release](./10-announce-release.md)
+9. [Update OTEL Contrib](./11-update-otel.md)
 
 ## Patch Release Publish (latest version)
 1. [Cherry Pick Commits](./2-cherry-pick-commits.md)
 2. [Update Version in Code](./3-update-version-in-code.md)
 3. [Tag Release](./4-tag-release.md)
 4. [Publish Release](./6-publish-release.md)
 5. [Update Helm Charts](./8-update-helm-charts.md)
-6. [Announce Release](./9-announce-release.md)
+6. [Update Homebrew](./9-update-homebrew.md)
+7. [Announce Release](./10-announce-release.md)
 
 ## Patch Release Publish (older version)
 - Not documented yet (but here are some hints)