doc: start v2.4 release notes draft

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

doc/release_notes/release_notes_2.4.rst

@@ -0,0 +1,91 @@
+.. _release_notes_2.4:
+
+ACRN v2.4 (Mar 2021) - DRAFT
+############################
+
+We are pleased to announce the release of the Project ACRN
+hypervisor version 2.4.
+
+ACRN is a flexible, lightweight reference hypervisor that is built with
+real-time and safety-criticality in mind. It is optimized to streamline
+embedded development through an open source platform. Check out the
+:ref:`introduction` introduction for more information.  All project ACRN
+source code is maintained in the
+https://github.com/projectacrn/acrn-hypervisor repository and includes
+folders for the ACRN hypervisor, the ACRN device model, tools, and
+documentation. You can either download this source code as a zip or
+tar.gz file (see the `ACRN v2.4 GitHub release page
+<https://github.com/projectacrn/acrn-hypervisor/releases/tag/v2.4>`_) or
+use Git clone and checkout commands::
+
+   git clone https://github.com/projectacrn/acrn-hypervisor
+   cd acrn-hypervisor
+   git checkout v2.4
+
+The project's online technical documentation is also tagged to
+correspond with a specific release: generated v2.4 documents can be
+found at https://projectacrn.github.io/2.4/.  Documentation for the
+latest under-development branch is found at
+https://projectacrn.github.io/latest/.
+
+ACRN v2.4 requires Ubuntu 18.04.  Follow the instructions in the
+:ref:`rt_industry_ubuntu_setup` to get started with ACRN.
+
+
+What's New in v2.4
+******************
+
+ACRN Configuration and Build
+============================
+
+[Add a short description of the changes to the ACRN configuration and build
+process that no longer uses Kconfig and relies on XML files, and refer them to
+the updated building from source and configuration options documents]
+
+Document Updates
+****************
+
+New and updated reference documents are available, including:
+
+.. rst-class:: rst-columns2
+
+* :ref:`APL_GVT-g-hld`
+* :ref:`hld-devicemodel`
+* :ref:`hld-trace-log`
+* :ref:`hld-virtio-devices`
+* :ref:`hv-cpu-virt`
+* :ref:`IOC_virtualization_hld`
+* :ref:`partition-mode-hld`
+* :ref:`hv-vm-management`
+* :ref:`vt-d-hld`
+* :ref:`virtio-console`
+* :ref:`virtio-i2c`
+* :ref:`rt_industry_ubuntu_setup`
+* :ref:`introduction`
+* :ref:`scenario-config-options`
+* :ref:`how-to-enable-acrn-secure-boot-with-grub`
+* :ref:`acrn_configuration_tool`
+* :ref:`acrn_doc`
+* :ref:`gpu-passthrough`
+* :ref:`rt_performance_tuning`
+* :ref:`setup_openstack_libvirt`
+* :ref:`using_windows_as_uos`
+* :ref:`vuart_config`
+* :ref:`acrn-dm_parameters`
+* :ref:`kernel-parameters`
+
+Because we dropped deprivileged boot mode support (in v2.3), we also
+switched our Service VM of choice away from Clear Linux and have
+removed Clear Linux-specific tutorials.  Deleted documents are still
+available in the `version-specific v2.1 documentation
+<https://projectacrn.github.io/v2.1/>`_.
+
+
+Fixed Issues Details
+********************
+
+.. example - :acrn-issue:`4958` - clean up spin lock for hypervisor
+
+Known Issues
+************
+