doc: redirect to 2.1 version for delete docs

As we're removing Clear Linux docs because of removing depriviliged boot
mode support, we can refer folks to the last known version of these docs
in the v2.1 release instead of just throwing a 404 error.

Signed-off-by: David B. Kinder <david.b.kinder@intel.com>

doc/conf.py

@@ -326,5 +326,22 @@ html_redirect_pages = [
    ('user-guides/index', 'develop'),
    ('hardware', 'reference/hardware'),
    ('release_notes', 'release_notes/index'),
-   ('getting-started/rt_industry', 'tutorials/cl_servicevm')
+   ('getting-started/rt_industry', 'tutorials/cl_servicevm'),
+   ('tutorials/acrn-dm_QoS', 'nocl'),
+   ('tutorials/acrn_ootb', 'nocl'),
+   ('tutorials/agl-vms', 'nocl'),
+   ('tutorials/building_acrn_in_docker', 'nocl'),
+   ('tutorials/building_uos_from_clearlinux', 'nocl'),
+   ('tutorials/cl_servicevm', 'nocl'),
+   ('tutorials/enable_laag_secure_boot', 'nocl'),
+   ('tutorials/increase_uos_disk_size', 'nocl'),
+   ('tutorials/kbl-nuc-sdc', 'nocl'),
+   ('tutorials/open_vswitch', 'nocl'),
+   ('tutorials/running_deb_as_serv_vm', 'nocl'),
+   ('tutorials/sign_clear_linux_image', 'nocl'),
+   ('tutorials/static-ip', 'nocl'),
+   ('tutorials/up2', 'nocl'),
+   ('tutorials/using_celadon_as_uos', 'nocl'),
+   ('tutorials/using_sbl_on_up2', 'nocl'),
+   ('tutorials/using_ubuntu_as_sos', 'nocl'),
    ]

doc/nocl.rst

@@ -0,0 +1,26 @@
+:orphan:
+
+.. comment This page is a common place holder for references to /latest/
+   documentation that was removed from the 2.2 release but there are
+   lingering references to these docs out in the wild and in the Google
+   index. Give the reader a reference to the /2.1/ document instead.
+
+This document was removed
+#########################
+
+.. raw:: html
+
+    <script>
+       document.write("<p>The document you tried to access is " +
+         "obsolete and was removed, but can still be found " +
+         "<a href=\"" +
+          document.referrer.replace("/latest/","/2.1/") +
+          "\">here in the v2.1 documentation</a> archive.</p>")
+    </script>
+
+
+In ACRN v2.2, deprivileged boot mode is no longer the default and will
+be completely removed in ACRN v2.3. We're focusing instead on using
+multiboot2 boot (via Grub). Multiboot2 is not supported in Clear Linux
+though, so we're removing Clear Linux as the Service VM of choice and
+with that, tutorial documentation about Clear Linux.