doc: Deprecate building Linux kernel module from OVS source tree.

It is decided (1) to deprecate building the Linux kernel module
from the Open vSwitch source tree.

Update the NEWS and FAQ to provide notice.

1. https://mail.openvswitch.org/pipermail/ovs-dev/2020-December/378831.html

Signed-off-by: Greg Rose <gvrose8192@gmail.com>
Acked-by: Flavio Leitner <fbl@sysclose.org>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

Documentation/faq/releases.rst

@@ -85,6 +85,12 @@ Q: What Linux kernel versions does each Open vSwitch release work with?
     RHEL and CentOS 7 3.10 based kernels since they have diverged from the
     Linux kernel.org 3.10 kernels.
 
+    Starting with Open vSwitch 2.15, building the Linux kernel module from
+    the Open vSwitch source tree is deprecated.  It will not be updated to
+    support Linux versions later than 5.8.  We will remove the kernel module
+    source code from the Open vSwitch source tree for the Open vSwitch 2.18
+    release.
+
 Q: Are all features available with all datapaths?
 
     A: Open vSwitch supports different datapaths on different platforms.  Each
@@ -100,8 +106,9 @@ Q: Are all features available with all datapaths?
       feature.
 
     Linux OVS tree
-      The datapath implemented by the Linux kernel module distributed with the
-      OVS source tree.
+      The datapath implemented by the Linux kernel module distributed with
+      the OVS source tree. This datapath is deprecated starting with OVS
+      2.15.x and support capped at Linux kernel version 5.8.
 
     Userspace
       This datapath supports conventional system devices as well as

NEWS

@@ -54,6 +54,11 @@ Post-v2.14.0
        tearing down IPsec tunnels.
      * Add option '--no-restart-ike-daemon' to allow ovs-monitor-ipsec to start
        without restarting ipsec daemon.
+   - Building the Linux kernel module from the OVS source tree is deprecated
+     * Support for the Linux kernel is capped at version 5.8
+     * Only bug fixes for the Linux OOT kernel module will be accepted.
+     * The Linux kernel module will be fully removed from the OVS source tree
+       in OVS branch 2.18
 
 
 v2.14.0 - 17 Aug 2020