Update CONTRIBUTING.adoc (#5425)

* Update CONTRIBUTING.adoc

* Update docs/CONTRIBUTING.adoc

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* Update docs/CONTRIBUTING.adoc

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/docs/CONTRIBUTING.adoc

@@ -25,9 +25,10 @@ Merging pull requests once CI is successful:
 	- it does not alter any logic (e.g. comments, dependencies, docs), then it may be tagged https://github.com/paritytech/substrate/pulls?utf8=%E2%9C%93&q=is%3Apr+is%3Aopen+label%3AA2-insubstantial[`insubstantial`] and merged by its author once CI is complete.
   - it is an urgent fix with no large change to logic, then it may be merged after a non-author contributor has approved the review once CI is complete.
 
-. Once a PR is ready for review please add the https://github.com/paritytech/substrate/pulls?q=is%3Apr+is%3Aopen+label%3AA0-pleasereview[`pleasereview`] label. Generally PRs should sit with this label for 48 hours in order to garner feedback. It may be merged before if all relevant parties had a look at it.
-. If the first review is not an approval, swap `A0-pleasereview` to any label `[A3, A7]` to indicate that the PR has received some feedback, but needs further work. For example. https://github.com/paritytech/substrate/labels/A3-inprogress[`A3-inprogress`] is a general indicator that the PR is work in progress and https://github.com/paritytech/substrate/labels/A4-gotissues[`A4-gotissues`] means that it has significant problems that need fixing. Once the work is done, change the label back to `A0-pleasereview`. You might end up swapping a few times back and forth to climb up the A label group. Once a PR is https://github.com/paritytech/substrate/labels/A8-looksgood[`A8-looksgood`], it is ready to merge. 
-. PRs that break the external API must be tagged with https://github.com/paritytech/substrate/labels/B2-breaksapi[`breaksapi`], when it changes the FRAME or consensus of running system with https://github.com/paritytech/substrate/labels/B3-breaksconsensus[`breaksconsensus`]
+. Once a PR is ready for review please add the https://github.com/paritytech/substrate/pulls?q=is%3Apr+is%3Aopen+label%3AA0-pleasereview[`A0-pleasereview`] label. Generally PRs should sit with this label for 48 hours in order to garner feedback. It may be merged before if all relevant parties had a look at it.
+. If the first review is not an approval, swap `A0-pleasereview` to any label `[A3, A7]` to indicate that the PR has received some feedback, but needs further work. For example. https://github.com/paritytech/substrate/labels/A3-inprogress[`A3-inprogress`] is a general indicator that the PR is work in progress and https://github.com/paritytech/substrate/labels/A4-gotissues[`A4-gotissues`] means that it has significant problems that need fixing. Once the work is done, change the label back to `A0-pleasereview`. You might end up swapping a few times back and forth to climb up the A label group. Once a PR is https://github.com/paritytech/substrate/labels/A8-mergeoncegreen[`A8-mergeoncegreen`], it is ready to merge. 
+. PRs must be tagged with respect to _release notes_ with https://github.com/paritytech/substrate/labels/B0-silent[`B0-silent`] and `B1-..`. The former indicates that no changes should be mentioned in any release notes. The latter indicates that the changes should be reported in the corresponding release note
+. PRs that break the external API must be tagged with https://github.com/paritytech/substrate/labels/B2-breaksapi[`B2-breaksapi`], when it changes the FRAME or consensus of running system with https://github.com/paritytech/substrate/labels/B3-breaksconsensus[`B3-breaksconsensus`]
 . No PR should be merged until all reviews' comments are addressed.
 
 *Reviewing pull requests*:
@@ -48,16 +49,19 @@ When reviewing a pull request, the end-goal is to suggest useful changes to the
 
 === Updating Polkadot as well
 
-If your PR changes the external APIs or interfaces used by Polkadot, **a corresponding PR on Polkadot must** be submitted as well. If you tagged the PR with `breaksapi` or `breaksconsensus` this is most certainly the case, in all other cases check for it by running step 1.
+**All pull requests will be checked agains either Polkadot master, or your provided Polkadot companion PR**. That is, If your PR changes the external APIs or interfaces used by Polkadot. If you tagged the PR with `breaksapi` or `breaksconsensus` this is most certainly the case, in all other cases check for it by running step 1 below.
 
-To update a corresponding Polkadot PR:
+To create a Polkadot companion PR:
 
-0. Pull latest Polkadot master (or clone it, if you haven't yet).
-1. Replace `polkadot-master` in all `Cargo.toml` with the name of the PR-branch - e.g. by running `find . -name "Cargo.toml" -exec sed -i "s/polkadot-master/PR_BRANCH/g" {}` (and to your repo, if the branch is not on mainline); Commit this change.
-2. Make the changes required to pass the build again.
-3. Submit all this as a PR against the Polkadot Repo, link that new PR in the existing substrate PR for reference
-4. Wait for reviews on both
-5. Once both PRs have been green lit, merge the Substrate PR into master and sync the changes onto the `polkadot-master` on mainline (push it). Now revert that first commit in your Polkadot PR, reverting the name back to `polkadot-master`, push and wait for the CI to confirm all is fine. Then merge the Polkadot PR.
+. Pull latest Polkadot master (or clone it, if you haven't yet).
+. Override your local cargo config to point to your local substrate (pointing to your WIP branch): place `paths = ["path/to/substrate"]` in `~/.cargo/config`.
+. Make the changes required and build polkadot locally.
+. Submit all this as a PR against the Polkadot Repo. Link to your Polkadot PR in the _description_ of your Substrate PR as "polkadot companion: [URL]". 
+. Now you should see that the `check_polkadot` CI job will build your Substrate PR agains the mentioned Polkadot branch in your PR description.
+. Wait for reviews on both
+. Once both PRs have been green lit, they can both be merged 🍻.  
+
+If your PR is reviewed well, but a Polkadot PR is missing, signal it with https://github.com/paritytech/substrate/labels/A7-needspolkadotpr[`A7-needspolkadotpr`] to prevent it from getting automatically merged. 
 
 As there might be multiple pending PRs that might conflict with one another, a) you should not merge the substrate PR until the Polkadot PR has also been reviewed and b) both should be merged pretty quickly after another to not block others.