doc: clarify rules for adding new built-in modules

Signed-off-by: Antoine du Hamel <duhamelantoine1995@gmail.com>
PR-URL: #64648
Reviewed-By: Filip Skokan <panva.ip@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Ulises Gascón <ulisesgascongonzalez@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Marco Ippolito <marcoippolito54@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jake Yuesong Li <jake.yuesong@gmail.com>
Reviewed-By: Richard Lau <richard.lau@ibm.com>

Author: aduh95

doc/contributing/collaborator-guide.md

@@ -443,10 +443,12 @@ metadata. Raise a pull request like any other change.
 
 Treat commits that introduce new core modules with extra care.
 
-New modules must only be added with the `node:` prefix.
+New modules must only be added with the `node:` prefix, as `semver-minor`.
 
-When adding promises to an existing API, add `/promises`
-(`inspector/promises`, etc.). Apply the `semver-major` label to the addition.
+When adding a "sub-module", e.g. a promise variant of an existing API (e.g.
+`node:inspector/promises`) that is available without the `node:` prefix, making
+the sub-module available without the prefix is possible behind a runtime flag,
+or as a `semver-major` change.
 
 If the new module name is free in npm, register
 a placeholder in the module registry as soon as possible. Link to the pull