docs: Add more details about the contribution process

Acked-by: Karol Herbst <kherbst@redhat.com>
Acked-by: Alyssa Rosenzweig <alyssa.rosenzweig@intel.com>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37233>

docs/submittingpatches.rst

@@ -1,6 +1,64 @@
 Submitting Patches
 ==================
 
+.. _introduction:
+
+Introduction
+------------
+
+Mesa contribution is a collaborative process that works like this:
+A contributor proposes a change (usually in the form of a GitLab
+merge request), which must undergo a review (usually in the form of
+comments from the maintainers on the merge request).
+
+The maintainers either accept it as-is, reject it outright,
+or request changes from the contributor before a contribution
+can be accepted.
+
+Mesa is a project that is made up of many different subprojects,
+for example drivers, API frontends, shader compiler infrastructure,
+etc. Each of these parts may have different maintainers and/or
+different rules and conventions. It is up to the maintainers of
+each specific part to decide what is acceptable for them and
+to direct the development of that part.
+
+.. _expectations_on_contributors:
+
+Expectations on contributors
+----------------------------
+
+Due to the collaborative nature of development, the expectation is that
+the contributor engages with the maintainers and works with
+us to shape the changeset into a form that can be accepted in the project.
+
+If you want to contribute code to Mesa, we highly recommend the following:
+
+-  Familiarize yourself with `Git <https://git-scm.com>`__.
+-  Understand the code you write at least well enough to be able
+   to explain why your changes are beneficial to the project.
+-  It's up you what tools you use to write code (development environment,
+   coding assistant, etc.), but keep in mind that no tool can substitute
+   actual understanding.
+
+In case you are not familiar with the code base, it's okay to ask for help
+and guidance from more experienced developers.
+
+The submitter is responsible for the code change, regardless of where
+that code change came from, whether they wrote it themselves, used an
+"AI" or other tool, or got it from someone else. That responsibility
+includes making sure that the code change can be submitted under the
+MIT license that Mesa uses.
+
+The submitter needs to understand what code they are changing,
+what the change does, and justify that change in the commit messages.
+Using coding assistants or "AI" or other tools does not grant additional
+privileges or reduce our expectations.
+
+If you don't know programming (and don't want to learn), but you are
+interested in the Mesa project, there are plenty of other ways to
+contribute besides writing code, for example reporting bugs, benchmarking,
+testing changes, etc.
+
 .. _guidelines:
 
 Basic guidelines
@@ -188,9 +246,26 @@ Submitting Patches
 ------------------
 
 Patches are submitted to the Mesa project via a
-`GitLab <https://gitlab.freedesktop.org/mesa/mesa>`__ Merge Request.
+`GitLab <https://gitlab.freedesktop.org/mesa/mesa>`__ Merge Request (MR).
 
-Add labels to your MR to help reviewers find it. For example:
+-  Please do NOT submit your patches in email to a mailing list,
+   we only review patches on GitLab.
+-  Please do NOT paste your patches as comments in a conversation,
+   unless it is small or unless that is what the maintainers requested.
+-  If you are not familiar with how to use git, please learn that
+   before making a contribution to Mesa.
+
+When opening a merge request, we recommend the following best practices:
+
+Add a prefix to the title of the MR to indicate which part of the
+codebase is affected. This is helpful to people who receive many MRs
+and filter them by title. All commits must also have a prefix.
+If you are unsure what is the correct prefix, please check the git
+history for the files you are changing and choose based on that.
+
+If you are already in the 'developer' role,
+add labels to your MR to help reviewers find your MR.
+For example:
 
 -  Mesa changes affecting all drivers: mesa
 -  Hardware vendor specific code: AMD common, intel, ...
@@ -198,6 +273,8 @@ Add labels to your MR to help reviewers find it. For example:
    vc4, ...
 -  Other tag examples: gallium, util
 
+If you don't add any labels, a bot will attempt to add the correct ones.
+
 Tick the following when creating the MR. It allows developers to rebase
 your work on top of main.