doc: update v2.5 release notes highlights

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

doc/release_notes/release_notes_2.5.rst

@@ -36,25 +36,37 @@ ACRN v2.5 requires Ubuntu 18.04.  Follow the instructions in the
 What's New in v2.5
 ******************
 
+- A brand-new concept, nested virtualization, is introduced as a preview in this
+  v2.5 release. It's designed to leverage KVM/Qemu community's rich feature set
+  while keeping ACRN's unique advantages in partition mode and hybrid mode. Read
+  more in the :ref:`nested_virt` advanced guide.
 
-ACRN Configuration and Build
-============================
+- The v2.5 release supports the upcoming 12th generation of Intel |reg| Core |trade|
+  processor (codename Alder Lake)
 
-The following major changes on ACRN configuration and build process have been
-integrated into v2.5:
+- EFI stub, previously retired in favor of using direct boot, returns as an
+  alternative to end-to-end secure boot with Grub. The hypervisor, ServiceVM
+  kernel, and prelaunched VM kernel are packaged into a single blob,
+  ``acrn.efi``, as an EFI application, which can then be verified together by
+  the EFI BIOS. Read more in the
+  :ref:`how-to-enable-acrn-secure-boot-with-efi-stub` and
+  :ref:`how-to-enable-acrn-secure-boot-with-grub` advanced guides.
 
-- Change 1
-- Change 2
+- :ref:`ACRN hypervisor modularization <modularity>` has been improved to be more
+  scalable, including change to multiboot, interrupt handling, paging and memory
+  management, timers, and more.
+
+- The ACRN configuration and build process continues to evolve from the changes
+  made in the previous releases.  For instructions using
+  the build system, refer to :ref:`getting-started-building`. For an
+  introduction on the concepts and workflow of the configuration tools and
+  processes, refer to :ref:`acrn_configuration_tool`.
 
-For complete instructions to get started with the new build system, refer to
-:ref:`getting-started-building`. For an introduction on the concepts and
-workflow of the new configuration mechanism, refer to
-:ref:`acrn_configuration_tool`.
 
 Upgrading to v2.5 From Previous Releases
 ****************************************
 
-We highly recommended that you follow the instructions below to
+We highly recommended that you follow these instructions to
 upgrade to v2.5 from previous ACRN releases.
 
 Generate New Board XML
@@ -64,11 +76,12 @@ Board XML files, generated by ACRN board inspector, contain board information
 that is essential to build ACRN. Compared to previous versions, ACRN v2.5
 extends the schema of board XMLs to summarize board information more
 systematically. You must regenerate your board XML file using the new
-board inspector when you upgrade to ACRN v2.5.
+board inspector when you upgrade to ACRN v2.5 to get the additional information
+needed for configuration.
 
-To use the new board inspector, ensure you have Python >= 3.6 on the target
+Before using the new board inspector, ensure you have Python >= 3.6 on the target
 board and install the ``lxml`` PyPI package. Refer to :ref:`upgrade_python` for
-detailed steps to check and upgrade Python version. The ``lxml`` package can be
+detailed steps to check and upgrade your Python version. The ``lxml`` package can be
 installed by executing the following command:
 
 .. code-block:: bash
@@ -86,6 +99,8 @@ directory on the target, and run the board inspector tool using::
    sudo python3 cli.py <my_board_name>
 
 This will generate ``<my_board_name>.xml`` in the current working directory.
+You'll need to copy that XML file back to the host system to continue
+development.
 
 Add New Configuration Options
 =============================
@@ -107,8 +122,23 @@ Constraints on values of the following element has changed:
 Document Updates
 ****************
 
-With the changes to ACRN configuration noted above, we made substantial updates
-to the ACRN documentation around configuration and options, as listed here:
+With the changes to ACRN configuration noted above, we made updates
+to the ACRN documentation around configuration and options:
+
+.. rst-class:: rst-columns2
+
+* :ref:`acrn_configuration_tool`
+* :ref:`scenario-config-options`
+* :ref:`acrn-dm_parameters`
+* :ref:`kernel-parameters`
+
+Some new capabilities are documented here:
+
+* :ref:`nested_virt`
+* :ref:`enable-ptm`
+
+We've also made edits throughout the documentation to improve clarity,
+formatting, and presentation throughout the ACRN documentation:
 
 .. rst-class:: rst-columns2
 
@@ -125,21 +155,14 @@ to the ACRN documentation around configuration and options, as listed here:
 * :ref:`getting-started-building`
 * :ref:`gsg`
 * :ref:`hardware`
-* :ref:`acrn_configuration_tool`
 * :ref:`acrn_on_qemu`
 * :ref:`acrn_doc`
 * :ref:`enable_ivshmem`
-* :ref:`enable-ptm`
-* :ref:`nested_virt`
 * :ref:`running_deb_as_serv_vm`
 * :ref:`trusty-security-services`
 * :ref:`using_hybrid_mode_on_nuc`
 * :ref:`connect_serial_port`
-* :ref:`acrn-dm_parameters`
-* :ref:`kernel-parameters`
 
-We've also made edits throughout the documentation to improve clarity,
-formatting, and presentation throughout the ACRN documentation.
 
 Fixed Issues Details
 ********************