doc/rdm: clarification to change process

doc/memos/rdm0000.md

@@ -108,13 +108,17 @@ its status is changed to "active" and it is merged in the master branch of RIOT.
 Once merged into the master branch of RIOT, a memo is considered published.
 
 Small changes/clarifications may be subsequently PRed to improve a memo, using
-the same RDM number. In this case, a (monotonically increasing) revision number
-is issued and a changelog is added -- see Revision section in postamble below.
-
-Bigger changes should result in a new memo with another
-RDM number, deprecating the old memo. In this case, the deprecated memo must
-be modified such that its status indicates "deprecated by [RDM XXXX](./rdmXXXX.md)"
-where X is the RDM number of the new memo.
+the same RDM number. These are defined as: corrections to spelling,
+punctuation, or grammar; clarifications to individual phrases or diagrams
+without changing the intended meaning. In this case, a (monotonically
+increasing) revision number is issued and a changelog is added -- see Revision
+section in postamble below.
+
+Any other changes should result in a new memo with another RDM number,
+deprecating the old memo. In this case, the deprecated memo must be modified
+such that its status indicates "deprecated by [RDM XXXX](./rdmXXXX.md)" where X
+is the RDM number of the new memo. Note that a memo should not be published if
+there are expected changes, whether small or large.
 
 A dedicated directory in RIOT codebase (RIOT/doc/memos) contains all the memos.
 It is acceptable to add complementary content such as graphical elments
@@ -143,6 +147,7 @@ Matthias Wählisch for their comments and suggestions.
 
 ## Revision
 
+- Rev3: clarified allowed changes between revisions
 - Rev2: added title in metadata and specification of temporary RDM naming
 - Rev1: added text on non-compulsory nature of RDMs
 - Rev0: initial document