create staging/threadnetwork and add OWNERS

The `hardware/interfaces/staging/threadnetwork` folder contains the
unstable/unreleased `hardware/interfaces/threadnetwork` code which
are not supposed to be used in production. But vendors may start
verifying their hardware with the HAL interface.

This directory will be cleaned up when the stable Thread HAL interface
is added in `hardware/interfaces/threadnetwork` by version `V` or later.

Bug: 203492431
Change-Id: I0d6aee0666029fd17a94b3a46c51f43127db4759
diff --git a/staging/threadnetwork/OWNERS b/staging/threadnetwork/OWNERS
new file mode 100644
index 0000000..037215d
--- /dev/null
+++ b/staging/threadnetwork/OWNERS
@@ -0,0 +1,5 @@
+# Bug component: 1203089
+
+wgtdkp@google.com
+xyk@google.com
+zhanglongxia@google.com
diff --git a/staging/threadnetwork/README.md b/staging/threadnetwork/README.md
new file mode 100644
index 0000000..12104e5
--- /dev/null
+++ b/staging/threadnetwork/README.md
@@ -0,0 +1,12 @@
+# Staging threadnetwork HAL interface
+
+The directory includes the unstable/unreleased version of `hardware/interfaces/threadnetwork`
+code which should **NOT** be used in production. But vendors may start verifying their hardware
+with the HAL interface.
+
+This directory will be cleaned up when the stable Thread HAL interface is added in
+`hardware/interfaces/threadnetwork` by version `V` or later.
+
+More information about _Thread_:
+- https://www.threadgroup.org
+- https://openthread.io