Preps for 1.6.0-rc1

Update version fields, and add release notes for the 1.6.0-rc1 release.

Signed-off-by: David Brown <david.brown@linaro.org>
diff --git a/README.md b/README.md
index b5018cc..9ff247a 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@
 [coverity]: https://scan.coverity.com/projects/mcuboot
 [travis]: https://travis-ci.org/JuulLabs-OSS/mcuboot
 
-This is mcuboot version 1.5.0
+This is mcuboot version 1.6.0-rc1
 
 MCUboot is a secure bootloader for 32-bit MCUs. The goal of MCUboot is to
 define a common infrastructure for the bootloader, system flash layout on
diff --git a/docs/release-notes.md b/docs/release-notes.md
index 3aa12b9..339f38b 100644
--- a/docs/release-notes.md
+++ b/docs/release-notes.md
@@ -3,6 +3,35 @@
 - Table of Contents
 {:toc}
 
+## Version 1.6.0
+
+The 1.6.0 release of MCUboot adds support for the PSOC6 platform,
+X25519 encrypted images, rollback protection, hardware keys, and a
+shared boot record to communicate boot attestation information to
+later boot stages.  There are bug fixes, and associated imgtool
+updates as well.
+
+### About this release
+
+- Initial support for the Cypress PSOC6 plaformt.  This platform
+  builds using the Cypress SDK, which has been added as submodules.
+- CBOR decoding in serial recovery replaced by code generated from a
+  CDDL description.
+- Add support for X25519 encrypted images.
+- Add rollback protection.  There is support for a HW rollback counter
+  (which must be provided as part of the platform), as well as a SW
+  solution that protects against some types of rollback.
+- Add an optional boot record in shared memory to communicate boot
+  attributes to later-run code.
+- Add support for hardware keys.
+- Various fixes to work with the latest Zephyr version.
+
+### Security issues addressed
+
+- CVE-2020-7595 "xmlStringLenDecodeEntities in parser.c in libxml2
+  2.9.10 has an infinite loop in a certain end-of-file situation." Fix
+  by updating a dependency in documentation generation.
+
 ## Version 1.5.0
 
 The 1.5.0 release of MCUboot adds support for encrypted images using
diff --git a/repository.yml b/repository.yml
index 97b3485..33b5ac5 100644
--- a/repository.yml
+++ b/repository.yml
@@ -29,6 +29,7 @@
     "1.3.1": "v1.3.1"
     "1.4.0": "v1.4.0"
     "1.5.0": "v1.5.0"
+    "1.6.0": "v1.6.0-rc1"
 
     "0-dev": "0.0.0"        # master
     "0-latest": "1.5.0"     # latest stable release