[Docs] Explain how to propose an extension in Clang

clang/AreaTeamMembers.txt

@@ -0,0 +1,17 @@
+This is a list of the current Clang Area Team members.
+
+Chair
+-----
+Aaron Ballman
+[email protected] (email), AaronBallman (Discourse), AaronBallman (GitHub), AaronBallman (Discord)
+
+Secretary
+---------
+Reid Kleckner
+[email protected] (email), rnk (Discourse), rnk (GitHub), rnk (Discord)
+
+Other Members
+-------------
+Eli Friedman
+[email protected]> (email), efriedma-quic (Discourse), efriedma-quic (GitHub)
+

clang/www/get_involved.html

@@ -83,7 +83,7 @@ <h2 id="criteria">Contributing Extensions to Clang</h2>
 for Clang. The benefits of the extension need to be evaluated against
 these costs. The Clang project uses the following criteria for this
 evaluation:</p>
-
+<p>
 <ol>
   <li>Evidence of a significant user community: This is based on a number of
   factors, including an existing user community, the perceived likelihood that
@@ -133,7 +133,36 @@ <h2 id="criteria">Contributing Extensions to Clang</h2>
   support the extension and what level of support is expected. The impacted
   project communities need to agree with that plan.</li>
 </ol>
-
+</p>
+<p>
+The Clang community uses an RFC process to evaluate potential extensions for
+inclusion in the tool. First, write a post in the <code>Clang Frontend</code>
+category of <a href="https://discourse.llvm.org/c/clang/6">Discourse</a>. The
+title should include <code>[RFC]</code> so it is clear that it is a proposed
+change. The post should have detailed information about the change itself, the
+motivation for needing the change, how it addresses the criteria listed above,
+and any other relevant details the community should be aware of.
+</p>
+<p>
+The community will discuss the proposal in Discourse, asking questions about
+the proposal to improve their understanding and giving support or dissent for
+the idea. Eventually, consensus will be determined as to whether the proposal
+should proceed or be rejected. If a proposal receives little or no feedback,
+that typically means that the proposal is rejected due to lack of interest.
+</p>
+<p>
+Sometimes, a consensus position is unclear and the proposal author will need
+additional guidance on what next steps to take. In such a case, the Clang Area
+Team may get involved. The Clang Area Team secretary will proactively look for
+RFCs that appear to not have a clear path forward to add them to the team's
+agenda. If anyone would like to put an RFC onto the team's agenda explicitly,
+they can tag any one of the <a href="https://github.com/llvm/llvm-project/blob/main/clang/AreaTeamMembers.txt">
+Clang Area Team</a> members in a comment on the RFC to get their attention. The
+area team will host a meeting to discuss the RFC and determine next steps for
+the proposal. In the event no clear community consensus position seems likely
+to ever form, the Clang Area Team will make a final judgement call on whether
+the RFC will proceed or not. <!-- TODO: link to area team processes -->
+</p>
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