ANDROID: add README.md

Add md file to communicate requirements for patches submitted
to common kernel

Change-Id: I92c3d8a6c40d8a8e5e9cfc9cb42887a5a858faf9
Signed-off-by: Todd Kjos <[email protected]>

README.md

@@ -0,0 +1,142 @@
+# How do I submit patches to Android Common Kernels
+
+1. BEST: Make all of your changes to upstream Linux. If appropriate, backport to the stable releases.
+   These patches will be merged automatically in the corresponding common kernels. If the patch is already
+   in upstream Linux, post a backport of the patch that conforms to the patch requirements below.
+
+2. LESS GOOD: Develop your patches out-of-tree (from an upstream Linux point-of-view). Unless these are
+   fixing an Android-specific bug, these are very unlikely to be accepted unless they have been
+   coordinated with [email protected]. If you want to proceed, post a patch that conforms to the
+   patch requirements below.
+
+# Common Kernel patch requirements
+
+- All patches must conform to the Linux kernel coding standards and pass `script/checkpatch.pl`
+- Patches shall not break gki_defconfig or allmodconfig builds for arm, arm64, x86, x86_64 architectures
+(see  https://source.android.com/setup/build/building-kernels)
+- If the patch is not merged from an upstream branch, the subject must be tagged with the type of patch:
+`UPSTREAM:`, `BACKPORT:`, `FROMGIT:`, `FROMLIST:`, or `ANDROID:`.
+- All patches must have a `Change-Id:` tag (see https://gerrit-review.googlesource.com/Documentation/user-changeid.html)
+- If an Android bug has been assigned, there must be a `Bug:` tag.
+- All patches must have a `Signed-off-by:` tag by the author and the submitter
+
+Additional requirements are listed below based on patch type
+
+## Requirements for backports from mainline Linux: `UPSTREAM:`, `BACKPORT:`
+
+- If the patch is a cherry-pick from Linux mainline with no changes at all
+    - tag the patch subject with `UPSTREAM:`.
+    - add upstream commit information with a `(cherry-picked from ...)` line
+    - Example:
+        - if the upstream commit message is
+```
+        important patch from upstream
+
+        This is the detailed description of the important patch
+
+        Signed-off-by: Fred Jones <[email protected]>
+```
+        - then Joe Smith would upload the patch for the common kernel as
+```
+        UPSTREAM: important patch from upstream
+
+        This is the detailed description of the important patch
+
+        Signed-off-by: Fred Jones <[email protected]>
+
+        Bug: 135791357
+        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
+        (cherry-picked from c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
+        Signed-off-by: Joe Smith <[email protected]>
+```
+
+- If the patch requires any changes from the upstream version, tag the patch with `BACKPORT:`
+instead of `UPSTREAM:`.
+    - use the same tags as `UPSTREAM:`
+    - add comments about the changes under the `(cherry-picked from ...)` line
+    - Example:
+```
+        BACKPORT: important patch from upstream
+
+        This is the detailed description of the important patch
+
+        Signed-off-by: Fred Jones <[email protected]>
+
+        Bug: 135791357
+        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
+        (cherry-picked from c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
+        [ Resolved minor conflict in drivers/foo/bar.c ]
+        Signed-off-by: Joe Smith <[email protected]>
+```
+
+## Requirements for other backports: `FROMGIT:`, `FROMLIST:`,
+
+- If the patch has been merged into an upstream maintainer tree, but has not yet
+been merged into Linux mainline
+    - tag the patch subject with `FROMGIT:`
+    - add info on where the patch came from as `(cherry picked from commit <sha1> <repo> <branch>)`. This
+must be a stable maintainer branch (not rebased, so don't use `linux-next` for example).
+    - if changes were required, use `BACKPORT: FROMGIT:`
+    - Example:
+        - if the commit message in the maintainer tree is
+```
+        important patch from upstream
+
+        This is the detailed description of the important patch
+
+        Signed-off-by: Fred Jones <[email protected]>
+```
+        - then Joe Smith would upload the patch for the common kernel as
+```
+        FROMGIT: important patch from upstream
+
+        This is the detailed description of the important patch
+
+        Signed-off-by: Fred Jones <[email protected]>
+
+        Bug: 135791357
+        (cherry picked from commit 878a2fd9de10b03d11d2f622250285c7e63deace
+         https://git.kernel.org/pub/scm/linux/kernel/git/foo/bar.git test-branch)
+        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
+        Signed-off-by: Joe Smith <[email protected]>
+```
+
+
+- If the patch has been submitted to LKML, but not accepted into any maintainer tree
+    - tag the patch subject with `FROMLIST:`
+    - add a `List:` tag with a link to the submittal on lore.kernel.org
+    - if changes were required, use `BACKPORT: FROMLIST:`
+    - Example:
+```
+        FROMLIST: important patch from upstream
+
+        This is the detailed description of the important patch
+
+        Signed-off-by: Fred Jones <[email protected]>
+
+        Bug: 135791357
+        Link: https://lore.kernel.org/lkml/[email protected]/
+        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
+        Signed-off-by: Joe Smith <[email protected]>
+```
+
+## Requirements for Android-specific patches: `ANDROID:`
+
+- If the patch is fixing a bug to Android-specific code
+    - tag the patch subject with `ANDROID:`
+    - add a `Fixes:` tag that cites the patch with the bug
+    - Example:
+```
+        ANDROID: fix android-specific bug in foobar.c
+
+        This is the detailed description of the important fix
+
+        Fixes: 1234abcd2468 ("foobar: add cool feature")
+        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
+        Signed-off-by: Joe Smith <[email protected]>
+```
+
+- If the patch is a new feature
+    - tag the patch subject with `ANDROID:`
+    - add a `Bug:` tag with the Android bug (required for android-specific features)
+