Add more documentation

Signed-off-by: Alexey Gladkov <[email protected]>

Documentation/Contributing.md

@@ -7,3 +7,50 @@ Here are some important resources:
 
 * [Mailing list](https://lists.altlinux.org/mailman/listinfo/make-initrd).
 * Bugs? Use [github](https://github.com/osboot/make-initrd/issues) to report them.
+
+
+**make-initrd** uses the linux kernel model where git is not only source repository,
+but also the way to track contributions and copyrights.
+
+Each submitted patch must have a "Signed-off-by" line.  Patches without
+this line will not be accepted.
+
+The sign-off is a simple line at the end of the explanation for the
+patch, which certifies that you wrote it or otherwise have the right to
+pass it on as an open-source patch.  The rules are pretty simple: if you
+can certify the below:
+```
+
+    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.
+
+```
+then you just add a line saying ( git commit -s )
+
+    Signed-off-by: Random J Developer <[email protected]>
+
+using your real name (sorry, no pseudonyms or anonymous contributions.)
+