docs: rSTify the "SubmitAPullRequest" wiki

The original wiki is here[1].  I converted by copying the wiki source
into a .wiki file and convert to rST using `pandoc`:

    $ pandoc -f Mediawiki -t rst submitting-a-pull-request.wiki \
        -o submitting-a-pull-request.rst

This is a 1-1 conversion; no content changes.

[1] https://wiki.qemu.org/Contribute/SubmitAPullRequest



Signed-off-by: Kashyap Chamarthy <kchamart@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20211110144902.388183-3-kchamart@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

docs/devel/index.rst

@@ -46,3 +46,4 @@ modifying QEMU's source code.
    qapi-code-gen
    writing-monitor-commands
    trivial-patches
+   submitting-a-pull-request

docs/devel/submitting-a-pull-request.rst

+Submit a Pull Request
+=====================
+
+QEMU welcomes contributions of code, but we generally expect these to be
+sent as simple patch emails to the mailing list (see our page on
+`submitting a patch
+<https://qemu-project.gitlab.io/qemu/devel/submitting-a-patch.html>`__
+for more details).  Generally only existing submaintainers of a tree
+will need to submit pull requests, although occasionally for a large
+patch series we might ask a submitter to send a pull request. This page
+documents our recommendations on pull requests for those people.
+
+A good rule of thumb is not to send a pull request unless somebody asks
+you to.
+
+**Resend the patches with the pull request** as emails which are
+threaded as follow-ups to the pull request itself. The simplest way to
+do this is to use ``git format-patch --cover-letter`` to create the
+emails, and then edit the cover letter to include the pull request
+details that ``git request-pull`` outputs.
+
+**Use PULL as the subject line tag** in both the cover letter and the
+retransmitted patch mails (for example, by using
+``--subject-prefix=PULL`` in your ``git format-patch`` command). This
+helps people to filter in or out the resulting emails (especially useful
+if they are only CC'd on one email out of the set).
+
+**Each patch must have your own Signed-off-by: line** as well as that of
+the original author if the patch was not written by you. This is because
+with a pull request you're now indicating that the patch has passed via
+you rather than directly from the original author.
+
+**Don't forget to add Reviewed-by: and Acked-by: lines**. When other
+people have reviewed the patches you're putting in the pull request,
+make sure you've copied their signoffs across. (If you use the `patches
+tool <https://github.com/stefanha/patches>`__ to add patches from email
+directly to your git repo it will include the tags automatically; if
+you're updating patches manually or in some other way you'll need to
+edit the commit messages by hand.)
+
+**Don't send pull requests for code that hasn't passed review**. A pull
+request says these patches are ready to go into QEMU now, so they must
+have passed the standard code review processes. In particular if you've
+corrected issues in one round of code review, you need to send your
+fixed patch series as normal to the list; you can't put it in a pull
+request until it's gone through. (Extremely trivial fixes may be OK to
+just fix in passing, but if in doubt err on the side of not.)
+
+**Test before sending**. This is an obvious thing to say, but make sure
+everything builds (including that it compiles at each step of the patch
+series) and that "make check" passes before sending out the pull
+request. As a submaintainer you're one of QEMU's lines of defense
+against bad code, so double check the details.
+
+**All pull requests must be signed**. If your key is not already signed
+by members of the QEMU community, you should make arrangements to attend
+a `KeySigningParty <https://wiki.qemu.org/KeySigningParty>`__ (for
+example at KVM Forum) or make alternative arrangements to have your key
+signed by an attendee.  Key signing requires meeting another community
+member \*in person\* so please make appropriate arrangements.  By
+"signed" here we mean that the pullreq email should quote a tag which is
+a GPG-signed tag (as created with 'gpg tag -s ...').
+
+**Pull requests not for master should say "not for master" and have
+"PULL SUBSYSTEM whatever" in the subject tag**. If your pull request is
+targeting a stable branch or some submaintainer tree, please include the
+string "not for master" in the cover letter email, and make sure the
+subject tag is "PULL SUBSYSTEM s390/block/whatever" rather than just
+"PULL". This allows it to be automatically filtered out of the set of
+pull requests that should be applied to master.
+
+You might be interested in the `make-pullreq
+<https://git.linaro.org/people/peter.maydell/misc-scripts.git/tree/make-pullreq>`__
+script which automates some of this process for you and includes a few
+sanity checks. Note that you must edit it to configure it suitably for
+your local situation!