docs: Update release notes for 2.0.0-rc1

Collect release notes, and add a bit about the API change.

Signed-off-by: David Brown <david.brown@linaro.org>
diff --git a/docs/release-notes.md b/docs/release-notes.md
index 00bb626..2fc96f7 100644
--- a/docs/release-notes.md
+++ b/docs/release-notes.md
@@ -3,6 +3,68 @@
 - Table of Contents
 {:toc}
 
+## Version 2.0.0
+
+Note that this release, 2.0.0 is a new major number, and contains a small API
+change in the interface between mcuboot and the platform.  All platforms
+contained within the MCUboot tree have been updated, but any external platforms
+will have to be adjusted.  The following commit makes the API change, in the
+function `boot_save_shared_data`.
+
+    commit 3016d00cd765e7c09a14af55fb4dcad945e4b982
+    Author: Jamie McCrae <jamie.mccrae@nordicsemi.no>
+    Date:   Tue Mar 14 12:35:51 2023 +0000
+    
+        bootutil: Add active slot number and max app size to shared data
+
+### About this release
+
+- Add error when flash device fails to open.
+- Panic bootloader when flash device fails to open.
+- Fixed issue with serial recovery not showing image details for
+  decrypted images.
+- Fixes issue with serial recovery in single slot mode wrongly
+  iterating over 2 image slots.
+- CDDL auto-generated function code has been replaced with zcbor function
+  calls, this now allows the parameters to be supplied in any order.
+- Added currently running slot ID and maximum application size to
+  shared data function definition.
+- Make the ECDSA256 TLV curve agnostic and rename it to ECDSA_SIG.
+- imgtool: add P384 support along with SHA384.
+- espressif: refactor after removing IDF submodule
+- espressif: add ESP32-C6, ESP32-C2 and ESP32-H2 new chips support
+- espressif: adjustments after IDF v5.1 compatibility, secure boot build and memory map organization
+- Serial recovery image state and image set state optional commands added
+- imgtool: add 'dumpinfo' command for signed image parsing.
+- imgtool: add 'getpubhash' command to dump the sha256 hash of the public key
+- imgtool's getpub can print the output to a file
+- imgtool can dump the raw versions of the public keys
+- Drop ECDSA P224 support
+- Fixed an issue with boot_serial repeats not being processed when
+  output was sent, this would lead to a divergence of commands
+  whereby later commands being sent would have the previous command
+  output sent instead.
+- Fixed an issue with the boot_serial zcbor setup encoder function
+  wrongly including the buffer address in the size which caused
+  serial recovery to fail on some platforms.
+- zcbor library files have been updated to version 0.7.0
+- Reworked boot serial extensions so that they can be used by modules
+  or from user repositories by switching to iterable sections.
+- Removed Zephyr custom img list boot serial extension support.
+- (Zephyr) Adds support for sharing boot information with
+  application via retention subsystem
+- Zephyr no longer builds in optimize for debug mode, this saves a
+  significant amount of flash space.
+- Reworked image encryption support for Zephyr, static dummy key files
+  are no longer in the code, a pem file must be supplied to extract
+  the private and public keys. The Kconfig menu has changed to only
+  show a single option for enabling encryption and selecting the key
+  file.
+- Serial recovery can now read and handle encrypted seondary slot
+  partitions.
+- Serial recovery with MBEDTLS no longer has undefined operations which
+  led to usage faults when the secondary slot image was encrypted.
+
 ## Version 1.10.0
 
 The 1.10.0 release of MCUboot contains...