Add module upgrade documentation page

Fixes: QTBUG-95307
Change-Id: Ifc5d59348d5f4c521e22a1aa7a30cef2f8dd57dd
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
(cherry picked from commit 002bbb637c25fac1617f8cd635ceca0fda62264b)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

2 files changed, 58 insertions, 0 deletions

diff --git a/src/charts/doc/src/index.qdoc b/src/charts/doc/src/index.qdoc
index 92f75ea7..ab35d16b 100644
--- a/src/charts/doc/src/index.qdoc
+++ b/src/charts/doc/src/index.qdoc
@@ -59,6 +59,10 @@
     \snippet doc_src_qtcharts.pro 0
     \endif
 
+    \section1 Module Evolution
+    \l{Changes to Qt Charts} lists important changes in the module API
+    and functionality that were done for the Qt 6 series of Qt.
+
     \section1 Licenses
 
     Qt Charts is available under commercial licenses from \l{The Qt Company}.
diff --git a/src/charts/doc/src/qt6-changes.qdoc b/src/charts/doc/src/qt6-changes.qdoc
new file mode 100644
index 00000000..74f24dbe
--- /dev/null
+++ b/src/charts/doc/src/qt6-changes.qdoc
@@ -0,0 +1,54 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the documentation of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:FDL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Free Documentation License Usage
+** Alternatively, this file may be used under the terms of the GNU Free
+** Documentation License version 1.3 as published by the Free Software
+** Foundation and appearing in the file included in the packaging of
+** this file. Please review the following information to ensure
+** the GNU Free Documentation License version 1.3 requirements
+** will be met: https://www.gnu.org/licenses/fdl-1.3.html.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+    \page qtcharts-changes-qt6.html
+    \title Changes to Qt Charts
+    \ingroup changes-qt-5-to-6
+    \brief Migrate Qt Charts to Qt 6.
+
+    Qt 6 is a result of the conscious effort to make the framework more
+    efficient and easy to use.
+
+    We try to maintain binary and source compatibility for all the public
+    APIs in each release. But some changes were inevitable in an effort to
+    make Qt a better framework.
+
+    In this document we summarize those changes in Qt Charts.
+
+    \section1 QtCharts Namespace
+
+    Qt Charts no longer has a custom \c QtCharts namespace. Instead, the normal Qt
+    namespace is used if one is configured for the Qt build.
+
+    \section1 OpenGL Acceleration in QML
+
+    As the name implies, \l{AbstractSeries::useOpenGL}{AbstractSeries.useOpenGL} still only
+    supports OpenGL acceleration, so it won't work if QML RHI backend is defined as something
+    else, as it typically is by default in Qt 6. Force RHI OpenGL backend into use to fix this
+    issue by using the environment variable \c{QSG_RHI_BACKEND=opengl}, for example.
+*/