doc: add review guidelines for collaborator nominations

PR-URL: #57449
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Marco Ippolito <marcoippolito54@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
Reviewed-By: Paolo Insogna <paolo@cowtech.it>
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: Ulises Gascón <ulisesgascongonzalez@gmail.com>

Author: aduh95

GOVERNANCE.md

@@ -287,6 +287,34 @@ from stalling indefinitely or objections from being overridden by the TSC.
 Remember that all private discussions about a nomination will be visible to
 the nominee once they are onboarded.
 
+#### How to review a collaborator nomination
+
+A collaborator nomination can be reviewed in the same way one would review a PR
+adding a feature:
+
+* If you see the nomination as something positive to the project, say so!
+* If you are neutral, or feel you don't know enough to have an informed opinion,
+  it's certainly OK to not interact with the nomination.
+* If you think the nomination was made too soon, or can be detrimental to the
+  project, share your concerns, ideally before the public nomination is opened,
+  and avoid sharing those concerns outside of the Collaborator discussion area.
+  Ideally, list what step(s) the nominee could take that would make you
+  approve their nomination.
+  Given that there is no "Request for changes" feature in discussions and issues,
+  try to be explicit when your comment is expressing a blocking concern.
+  Similarly, once the blocking concern has been addressed, explicitly say so.
+
+Our goal is to keep gate-keeping at a minimal, but it cannot be zero since being
+a collaborator requires trust (collaborators can start CI jobs, use their veto,
+push commits, etc.), so what's the minimal amount is subjective, and there will
+be cases where collaborators disagree on whether a nomination should move
+forward.
+
+When concerns have been raised on the private discussion, refrain from opening
+the public issue. If no one has explicitly blocked the nomination and you'd like
+it to move forward, comment something like "If I don't hear any objections
+before (some time), I will open the public issue".
+
 ### Onboarding
 
 After the nomination passes, a TSC member onboards the new collaborator. See