[llvm] Document the community RFC process (PR #116386)

[Aaron Ballman via llvm-commits]

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+=================================
+Request For Comment (RFC) process
+=================================
+
+.. contents::
+   :local:
+   :depth: 1
+
+Introduction
+============
+Substantive changes to LLVM projects need to be acceptable to the wider
+community, which requires gaining community consensus to adopt the changes.
+This is done by posting an RFC and obtaining feedback about the proposal.
+
+Process
+=======
+
+Writing an RFC
+--------------
+The process begins with writing a proposal for the changes you'd like to see
+made. The proposal should include:
+
+* a detailed overview of the proposed changes,
+* the motivation for why the changes are being proposed,
+* the impact on different parts of the project, and
+* any open questions the community should address.
+
+The proposal should be posted to the appropriate forum on
+`Discourse <https://discourse.llvm.org/>`_.
+
+Feedback Period
+---------------
+Once the RFC is posted, the community will provide feedback on the proposal.
+The feedback period is a collaborative effort between the community and the
+proposal authors. Authors should take the community's feedback into
+consideration and edit the original post to incorporate relevant changes they
+agree to. Edits should be made such that it's clear what has changed. Editing
+the original post makes it easier for the community to understand the proposal
+without having to read every comment on the thread, though this can make
+reading the comment thread somewhat more difficult as comments may be referring
+to words no longer in the proposal.
+
+There is not a set time limit to the feedback period; it lasts as long as
+discussion is actively continuing on the proposal.
+
+Trivial Acceptance or Rejection
+-------------------------------
+Some proposals have obvious consensus (for or against) after discussion in the
+community. It is acceptable to presume a post which appears to have obvious
+consensus has been accepted.
+
+Non-trivial Acceptance or Rejection
+-----------------------------------
+If the proposal has does not have obvious consensus after community discussion,
+a maintainer for each of the impacted parts of the project should explicitly
+accept or reject the RFC by leaving a comment stating their decision and
+possibly detailing any provisions for their acceptance. Overall consensus is
+determined once a maintainer from each impacted part of the project has
+accepted the proposal.
+
+Low Engagement Level
+~~~~~~~~~~~~~~~~~~~~
+If a proposal gets little or no engagement by the community, it is a sign that
----------------
AaronBallman wrote:

Good catches, I've addressed both things you spotted

https://github.com/llvm/llvm-project/pull/116386