[nrfconnect] add support for nRF5340 (#5161)

diff --git a/examples/lock-app/nrfconnect/README.md b/examples/lock-app/nrfconnect/README.md
index d606b37..857136b 100644
--- a/examples/lock-app/nrfconnect/README.md
+++ b/examples/lock-app/nrfconnect/README.md
@@ -5,9 +5,14 @@
 states and LEDs to show the state of these changes. You can use this example as
 a reference for creating your own application.
 
+<p align="center">
+  <img src="../../platform/nrfconnect/doc/images/Logo_RGB_H-small.png" alt="Nordic Semiconductor logo"/>
+  <img src="../../platform/nrfconnect/doc/images/nRF52840-DK-small.png" alt="nRF52840 DK">
+</p>
+
 The example is based on [CHIP](https://github.com/project-chip/connectedhomeip)
-and the nRF Connect platform, and supports remote access and control of a
-simulated door lock over a low-power, 802.15.4 Thread network.
+and Nordic Semiconductor's nRF Connect SDK, and supports remote access and
+control of a simulated door lock over a low-power, 802.15.4 Thread network.
 
 The example behaves as a CHIP accessory, that is a device that can be paired
 into an existing CHIP network and can be controlled by this network.
@@ -18,6 +23,7 @@
     -   [Bluetooth LE advertising](#bluetooth-le-advertising)
     -   [Bluetooth LE rendezvous](#bluetooth-le-rendezvous)
 -   [Requirements](#requirements)
+    -   [Supported devices](#supported_devices)
 -   [Device UI](#device-ui)
 -   [Setting up the environment](#setting-up-the-environment)
     -   [Using Docker container for setup](#using-docker-container-for-setup)
@@ -34,7 +40,8 @@
 
 ## Overview
 
-This example is running on the nRF Connect platform, which is based on the
+This example is running on the nRF Connect platform, which is based on Nordic
+Semiconductor's
 [nRF Connect SDK](https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/index.html)
 and [Zephyr RTOS](https://zephyrproject.org/). Visit CHIP's
 [nRF Connect platform overview](../../../docs/guides/nrfconnect_platform_overview.md)
@@ -84,11 +91,16 @@
 
 The application requires the nRF Connect SDK v1.5.0 to work correctly.
 
+<a name="supported_devices"></a>
+
+### Supported devices
+
 The example supports building and running on the following devices:
 
-| Board name                                                                                | Board platform build name |
-| ----------------------------------------------------------------------------------------- | ------------------------- |
-| [nRF52840 DK](https://www.nordicsemi.com/Software-and-Tools/Development-Kits/nRF52840-DK) | `nrf52840dk_nrf52840`     |
+| Hardware platform                                                                         | Build target               | Platform image                                                                                                                                      |
+| ----------------------------------------------------------------------------------------- | -------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------- |
+| [nRF52840 DK](https://www.nordicsemi.com/Software-and-Tools/Development-Kits/nRF52840-DK) | `nrf52840dk_nrf52840`      | <details><summary>nRF52840 DK</summary><img src="../../platform/nrfconnect/doc/images/nRF52840-DK_top-view-small.jpg" alt="nRF52840 DK"/></details> |
+| [nRF5340 DK](https://www.nordicsemi.com/Software-and-Tools/Development-Kits/nRF5340-DK)   | `nrf5340dk_nrf5340_cpuapp` | <details><summary>nRF5340 DK</summary><img src="../../platform/nrfconnect/doc/images/nRF5340-DK_top-view-small.jpg" alt="nRF5340 DK"/></details>    |
 
 <hr>
 
@@ -97,10 +109,8 @@
 ## Device UI
 
 This section lists the User Interface elements that you can use to control and
-monitor the state of the device. All these elements can be located on the
-following board picture:
-
-![nrf52840 DK](../../platform/nrfconnect/doc/images/nrf52840-dk.jpg)
+monitor the state of the device. These correspond to PCB components on the
+platform image.
 
 **LED 1** shows the overall state of the device and its connectivity. The
 following states are possible:
@@ -171,7 +181,7 @@
 the tools pre-installed.
 
 If you are a macOS user, you won't be able to use the Docker container to flash
-the application onto a Nordic board due to
+the application onto a Nordic development kit due to
 [certain limitations of Docker for macOS](https://docs.docker.com/docker-for-mac/faqs/#can-i-pass-through-a-usb-device-to-a-container).
 Use the [native shell](#using-native-shell) for building instead.
 
@@ -271,20 +281,20 @@
 
         $ cd examples/lock-app/nrfconnect
 
-2.  Run the following command to build the example, with _board-name_ replaced
-    with the name of the Nordic Semiconductor's board you own, for example
-    `nrf52840dk_nrf52840`:
+2.  Run the following command to build the example, with _build-target_ replaced
+    with the build target name of the Nordic Semiconductor's kit you own, for
+    example `nrf52840dk_nrf52840`:
 
-         $ west build -b board-name
+         $ west build -b build-target
 
-    You only need to specify the board name on the first build. See
-    [Requirements](#requirements) for the names of compatible boards.
+    You only need to specify the build target on the first build. See
+    [Requirements](#requirements) for the build target names of compatible kits.
 
 The output `zephyr.hex` file will be available in the `build/zephyr/` directory.
 
 ### Removing build artifacts
 
-If you're planning to build the example for a different board or make changes to
+If you're planning to build the example for a different kit or make changes to
 the configuration, remove all build artifacts before building. To do so, use the
 following command:
 
@@ -295,10 +305,10 @@
 To build the example with release configuration that disables the diagnostic
 features like logs and command-line interface, run the following command:
 
-    $ west build -b board-name -- -DOVERLAY_CONFIG=third_party/connectedhomeip/config/nrfconnect/app/release.conf
+    $ west build -b build-target -- -DOVERLAY_CONFIG=third_party/connectedhomeip/config/nrfconnect/app/release.conf
 
-Remember to replace _board-name_ with the name of the Nordic Semiconductor's
-board you own.
+Remember to replace _build-target_ with the build target name of the Nordic
+Semiconductor's kit you own.
 
 <hr>
 
@@ -312,10 +322,10 @@
 To open the menuconfig utility, run the following command from the example
 directory:
 
-    $ west build -b board-name -t menuconfig
+    $ west build -b build-target -t menuconfig
 
-Remember to replace _board-name_ with the name of the Nordic Semiconductor's
-board you own.
+Remember to replace _build-target_ with the build target name of the Nordic
+Semiconductor's kit you own.
 
 Changes done with menuconfig will be lost if the `build` directory is deleted.
 To make them persistent, save the configuration options in the `prj.conf` file.
@@ -334,7 +344,7 @@
 
         $ west flash
 
-If you have multiple nRF52840 DK boards connected, west will prompt you to pick
+If you have multiple development kits connected, west will prompt you to pick
 the correct one.
 
 To debug the application on target, run the following command from the example