doc: clarify that features cannot be both experimental and deprecated

PR-URL: #62456
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com>
Reviewed-By: Jacob Smith <jacob@frende.me>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

Author: aduh95

doc/contributing/collaborator-guide.md

@@ -387,6 +387,12 @@ undergo deprecation. The exceptions to this rule are:
 * Changes to errors thrown by dependencies of Node.js, such as V8.
 * One-time exceptions granted by the TSC.
 
+Experimental and undocumented APIs are not considered stable, therefore are
+typically removed without a deprecation cycle. However, if such API has gotten
+some non-trivial adoption in the ecosystem, it (or a subset of it) can undergo
+deprecation – at which point, changes to that API (or at least, its deprecated
+subset) should follow [semantic versioning][] rules.
+
 For more information, see [Deprecations](#deprecations).
 
 #### Breaking changes to internal elements
@@ -526,8 +532,8 @@ the three Deprecation levels. Documentation-Only Deprecations can land in a
 minor release. They can not change to a Runtime Deprecation until the next major
 release.
 
-No API can change to End-of-Life without going through a Runtime Deprecation
-cycle. There is no rule that deprecated code must progress to End-of-Life.
+No deprecated APIs can change to End-of-Life without going through a Runtime
+Deprecation cycle. There is no rule that deprecated code must progress to End-of-Life.
 Documentation-Only and Runtime Deprecations can remain in place for an unlimited
 duration.
 
@@ -1059,6 +1065,7 @@ need to be attached anymore, as only important bugfixes will be included.
 [node-core-utils-issues]: https://github.com/nodejs/node-core-utils/issues
 [ppc]: https://github.com/orgs/nodejs/teams/platform-ppc
 [s390]: https://github.com/orgs/nodejs/teams/platform-s390
+[semantic versioning]: https://semver.org/
 [smartos]: https://github.com/orgs/nodejs/teams/platform-smartos
 [unreliable tests]: https://github.com/nodejs/node/issues?q=is%3Aopen+is%3Aissue+label%3A%22CI+%2F+flaky+test%22
 [windows]: https://github.com/orgs/nodejs/teams/platform-windows