docs: add MAINTAINING.md (UMAprotocol#2492)

CONTRIBUTING.md

@@ -9,6 +9,7 @@ the process works smoothly and your contributions can be merged as quickly and e
 - If you are a maintainer and your review is requested, you are expected to either provide a review within 1 business
   day (in your time zone) or reassign the review to another maintainer.
 - The same expectations apply for follow-up reviews where your review is re-requested after an update has been made.
+- See [MAINTAINING.md](./MAINTAINING.md) for information about the responsibilities of the on-duty maintainer.
 
 ## Communication
 

MAINTAINING.md

@@ -0,0 +1,24 @@
+# Maintaining UMA Repositories
+
+As our repos grow in activity, it takes more and more effort to maintain them and ensure code and issues are being
+actively triaged for consideration and review. This document outlines the responsibilities of the on-duty maintainer.
+
+## Responsibilities
+
+- Every business day, the on-duty maintainer is expected to make a pass over _all_ open PRs and new issues in _all_
+  UMA repositories.
+  - On-duty maintainers rotate each week in a round robin fashion
+- For each PR, the on-duty maintainer should make sure the PR is moving forward:
+  - Check the title and description according to the [template](./.github/PULL_REQUEST_TEMPLATE.md). If either of
+    these are incorrect, edit them and add a comment explaining your edits.
+  - Make sure reviews are requested. If not, request them (if the PR is very small, feel free to just review it
+    yourself).
+  - If the PR has stalled, determine whose action is needed and tag them in a comment (or re-request a review if it's
+    the reviewer). If a 3rd party's PR is ready and passing tests, merge it.
+  - DCO is a common problem for many users, please help them by pointing them to the
+    [DCO docs](https://github.com/apps/dco). Note: DCO checks can be overriden for UMA org members because DCO is covered
+    by other agreements, but 3rd party developers _must_ sign off on their commits.
+  - For the full PR process, see [the contributing guidelines](./CONTRIBUTING.md).
+- For each _new_ issue:
+  - If it's a 3rd party issue, traige by assigning or tagging a relevant UMA team member.
+  - If it was posted by an UMA org member, no action is required.