Start skeleton release notes for the next version.

Restructured so that:

* 'Upgrading' is limited to work that has to be done to upgrade from
  a current deployment to the new version.

* 'Changes' is a comprehensive, user-level description of changes and
  new features.

Conflicts:
	doc/sphinx/whats-new/index.rst

doc/sphinx/whats-new/changes-trunk.rst

+..
+	Copyright 2021 Varnish Software
+	SPDX-License-Identifier: BSD-2-Clause
+	See LICENSE file for full text of license
+
+**Note: This is a working document for a future release, with running
+updates for changes in the development branch. For changes in the
+released versions of Varnish, see:** :ref:`whats-new-index`
+
+.. _whatsnew_changes_CURRENT:
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+Changes in Varnish **$NEXT_RELEASE**
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+For information about updating your current Varnish deployment to the
+new version, see :ref:`whatsnew_upgrading_CURRENT`.
+
+A more detailed and technical account of changes in Varnish, with
+links to issues that have been fixed and pull requests that have been
+merged, may be found in the `change log`_.
+
+.. _change log: https://github.com/varnishcache/varnish-cache/blob/master/doc/changes.rst
+
+varnishd
+========
+
+Parameters
+~~~~~~~~~~
+
+**XXX changes in -p parameters**
+
+Other changes in varnishd
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Changes to VCL
+==============
+
+VCL variables
+~~~~~~~~~~~~~
+
+**XXX new, deprecated or removed variables, or changed semantics**
+
+Other changes to VCL
+~~~~~~~~~~~~~~~~~~~~
+
+VMODs
+=====
+
+**XXX changes in the bundled VMODs**
+
+varnishlog
+==========
+
+**XXX changes concerning varnishlog(1) and/or vsl(7)**
+
+varnishadm
+==========
+
+**XXX changes concerning varnishadm(1) and/or varnish-cli(7)**
+
+varnishstat
+===========
+
+**XXX changes concerning varnishstat(1) and/or varnish-counters(7)**
+
+varnishtest
+===========
+
+**XXX changes concerning varnishtest(1) and/or vtc(7)**
+
+Changes for developers and VMOD authors
+=======================================
+
+**XXX changes concerning VRT, the public APIs, source code organization,
+builds etc.**
+
+*eof*

doc/sphinx/whats-new/index.rst

@@ -13,6 +13,19 @@ This section describes the changes and improvements between different
 versions of Varnish, and what upgrading between the different versions
 entail.
 
+Varnish **$NEXT_RELEASE**
+-------------------------
+
+**Note: These are working documents for a future release, with running
+updates for changes in the development branch. For changes in the
+released versions of Varnish, see the chapters listed below.**
+
+.. toctree::
+   :maxdepth: 2
+
+   changes-trunk
+   upgrading-trunk
+
 Varnish 6.6
 -----------
 

doc/sphinx/whats-new/upgrading-trunk.rst

+..
+	Copyright 2021 Varnish Software
+	SPDX-License-Identifier: BSD-2-Clause
+	See LICENSE file for full text of license
+
+**Note: This is a working document for a future release, with running
+updates for changes in the development branch. For changes in the
+released versions of Varnish, see:** :ref:`whats-new-index`
+
+.. _whatsnew_upgrading_CURRENT:
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+Upgrading to Varnish **$NEXT_RELEASE**
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+**XXX: how to upgrade from previous deployments to this
+version. Limited to work that has to be done for an upgrade, new
+features are listed in "Changes". Explicitly mention what does *not*
+have to be changed, especially in VCL. May include, but is not limited
+to:**
+
+* Elements of VCL that have been removed or are deprecated, or whose
+  semantics have changed.
+
+* -p parameters that have been removed or are deprecated, or whose
+  semantics have changed.
+
+* Changes in the CLI.
+
+* Changes in the output or interpretation of stats or the log, including
+  changes affecting varnishncsa/-hist/-top.
+
+* Changes that may be necessary in VTCs or in the use of varnishtest.
+
+* Changes in public APIs that may require changes in VMODs or VAPI/VUT
+  clients.
+
+*eof*