docs: Contribution guideline update

Explicitely mention that this project adheres to the Developer
Certificate of Origin (DCO) and include this short text.

Also reformat the file to have lines bounded at 80 chars and add some
more details regarding the expected commit message format.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>

1 files changed, 74 insertions, 13 deletions

diff --git a/docs/contributing.md b/docs/contributing.md
index a17c548..227c5c6 100644
--- a/docs/contributing.md
+++ b/docs/contributing.md
@@ -1,13 +1,74 @@
-OpenSBI Contributing Guidelines
-===============================
-
-All contributions to OpenSBI should be sent as GitHub Pull Requests (PRs) to the main repository avaliable at: https://github.com/riscv/opensbi
-
-As well as that all work must follow the following rules:
-1. We follow the [Linux coding style](https://www.kernel.org/doc/html/v4.10/process/coding-style.html). This means that ALL patches must include the Signed-off-by line.
-2. Commit subject must have at least one ":" prefix. Common ones are "lib:", "platform:", "firmware:", "docs:" and "top:".
-3. Maintainer should use "Rebase and Merge" when using GitHub to merge pull requests to avoid unnecessary merge commits.
-4. Maintainer should avoid creating branches directly in main riscv/opensbi repository. Instead prefer fork of GitHub riscv/opensbi repository and create branches in your own fork for pull requests.
-5. Maintainer cannot merge his own pull requests on GitHub.
-6. A pull request must get at least one review from relevant maintainer.
-7. A pull request must spend at least 24 hours in review so that everyone gets a chance to review.
+OpenSBI Contribution Guideline
+==============================
+
+All contributions to OpenSBI should be sent as GitHub Pull Requests (PRs) to
+[OpenSBI main repository].
+
+All contributed work must follow the following rules:
+1. OpenSBI code should be written in accordance to [Linux coding style].
+2. This project embraces the [Developer Certificate of Origin (DCO)] for
+contributions. This means that you must agree to the following prior to
+submitting patches: if you agree with this developer certificate you
+acknowledge this by adding a Signed-off-by tag to your patch commit log.
+Every submitted patch must have this tag.
+3. A commit message must have a subject line, followed by a blank line,
+followed by a description of the patch content. A blank line and the author
+Signed-off-by tag must follow this description.
+4. A commit subject line must start with a prefix followed by a ":". Common
+prefixes are for example "lib:", "platform:", "firmware:", "docs:" and "top:".
+5. Maintainers should use "Rebase and Merge" when using GitHub to merge pull
+requests to avoid creating unnecessary merge commits.
+6. Maintainers should avoid creating branches directly in the main
+riscv/opensbi repository. Instead prefer using a fork of riscv/opensbi main
+repository and branches within that fork to create pull requests.
+7. A maintainer cannot merge his own pull requests in riscv/opensbi main
+repository.
+8. A pull request must get at least one review from a maintainer.
+9. A pull request must spend at least 24 hours in review to allow for other
+developers to review.
+
+-----------------------------------------------------------------------
+
+Developer Certificate of Origin
+Version 1.1
+
+Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
+660 York Street, Suite 102,
+San Francisco, CA 94110 USA
+
+Everyone is permitted to copy and distribute verbatim copies of this
+license document, but changing it is not allowed.
+
+
+Developer's Certificate of Origin 1.1
+
+By making a contribution to this project, I certify that:
+
+(a) The contribution was created in whole or in part by me and I
+    have the right to submit it under the open source license
+    indicated in the file; or
+
+(b) The contribution is based upon previous work that, to the best
+    of my knowledge, is covered under an appropriate open source
+    license and I have the right under that license to submit that
+    work with modifications, whether created in whole or in part
+    by me, under the same open source license (unless I am
+    permitted to submit under a different license), as indicated
+    in the file; or
+
+(c) The contribution was provided directly to me by some other
+    person who certified (a), (b) or (c) and I have not modified
+    it.
+
+(d) I understand and agree that this project and the contribution
+    are public and that a record of the contribution (including all
+    personal information I submit with it, including my sign-off) is
+    maintained indefinitely and may be redistributed consistent with
+    this project or the open source license(s) involved.
+
+-----------------------------------------------------------------------
+
+[OpenSBI main repository]: https://github.com/riscv/opensbi
+[Linux coding style]: https://www.kernel.org/doc/html/v4.10/process/coding-style.html
+[Developer Certificate of Origin (DCO)]: http://developercertificate.org/
+