doc: add v2.5.1 release notes

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

doc/release_notes/release_notes_2.5.1.rst

@@ -0,0 +1,32 @@
+.. _release_notes_2.5.1:
+
+ACRN v2.5.1 (Aug 2021)
+######################
+
+We are pleased to announce an update release of the Project ACRN hypervisor
+version 2.5.1. This is a maintenance release based off the v2.5 branch that
+provides an update with a few bug fixes and support for Trusted Platform Module
+(TPM) 2.0.
+
+There were no documentation changes in this update, so you can still refer to
+the v2.5-specific documentation found at https://projectacrn.github.io/2.5/.
+
+See the :ref:`release_notes_2.5` release notes for information about the v2.5
+release.
+
+
+What's New in v2.5.1
+********************
+
+Trusted Platform Module (TPM) 2.0 support
+  ACRN hypervisor now supports pre-launched VM remote attestation use cases by
+  passing the TPM 2.0 ACPI table provided by the BIOS to the pre-launched VM.
+
+Fixed Issues Details
+********************
+
+.. comment example item
+   - :acrn-issue:`5626` - [CFL][industry] Host Call Trace once detected
+
+- :acrn-issue:`6305` - Pre-launched Zephyr VM coud not get ACPI table
+- :acrn-issue:`6334` - Hypervisor console does not support 64-bit bar PCI UART with 32-bit bar space