Add virtio-aarch64 platform description via scc file.

Metadata is based on qemuarm64-standard.scc from
yocto-kernel-cache branch yocto-5.15 commit
947149960e1426ace478e4b52c28a28ef8d6e74b with a lot of unended
configurations removed.

Comparing to initial version [1] many TODOs have been removed since
changes landed upstream (yocto-kernel-cache).

Note, that BSP description root file virtio-aarch64-standard.scc has to
be kept local withing a recipe. This is needed to add this scc file
explicitly to SRC_URI to have AGL VIRTIO patches applied during kernel
recipe build.

As explained in [2, 3], Yocto kernel metadata is commonly used for two
purposes:

1. To construct Yocto kernel git by committing patches listed in scc
files.
2. To configure Yocto kernel during Yocto build.

When scc file is not explicitly added to SRC_URI, then patch commands
will be ignored during Yocto build because it is assumed that patches
are already pre-applied during Yocto kernel git tree construction.

But, there is not AGL Linux kernel tree, only a repository for AGL
kernel metadata (this one). So, patches from this metadata repository
have to be applied during kernel recipe build.

[1]: https://gerrit.automotivelinux.org/gerrit/gitweb?p=AGL/meta-agl.git;a=commit;h=2d05cfff33a010c2133f66e757d2f4850c584a1e
[2]: https://www.yoctoproject.org/pipermail/yocto/2019-October/046986.html
[3]: https://docs.yoctoproject.org/kernel-dev/maint-appx.html

Bug-AGL: SPEC-4452
Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
Change-Id: Ic88a35ccbe4cad6e5b22bf43c687407f506c2e5b

1 files changed, 28 insertions, 0 deletions

diff --git a/README b/README
new file mode 100644
index 0000000..64e2cd0
--- /dev/null
+++ b/README
@@ -0,0 +1,28 @@
+agl-yocto-kernel-meta
+=====================
+
+Yocto Project kernel rich Metadata [1] for AGL based on YP's kernel rich
+metadata [2].
+
+Using Yocto Linux Kernel is recommended in "Yocto Project Board Support Package
+Developer's Guide" [3]:
+
+> Kernel recipes in the BSP should be based on a Yocto Linux kernel. Basing your
+> recipes on these kernels reduces the costs for maintaining the BSP and
+> increases its scalability.
+
+YP advanced kernel metadata besides configuration fragments and patches,
+realizes scc description files (scc stands for Series Configuration Control, but
+the naming has less significance in the current implementation of the tooling
+than it had in the past) which allow to:
+
+* group configuration fragments and patches into a reusable unit
+* include scc files from other scc files
+* besides BSP description scc file, additional scc files can be easily applied
+  by adding them to KERNEL_FEATURES variable
+
+and much more.
+
+[1]: https://docs.yoctoproject.org/4.0.2/kernel-dev/advanced.html
+[2]: https://git.yoctoproject.org/yocto-kernel-cache
+[3]: https://docs.yoctoproject.org/4.0.2/bsp-guide/bsp.html#released-bsp-recommendations