zephyr: Upgrade to Zephyr v4.2.0.

Updates the Zephyr port build instructions and CI to use the latest
Zephyr release tag.

Tested on max32690fthr and frdm_k64f.

Signed-off-by: Maureen Helm <maureen.helm@analog.com>

Author: MaureenHelm

docs/zephyr/tutorial/repl.rst

@@ -31,8 +31,8 @@ With your serial program open (PuTTY, screen, picocom, etc) you may see a
 blank screen with a flashing cursor. Press Enter (or reset the board) and
 you should be presented with the following text::
 
-        *** Booting Zephyr OS build v4.0.0 ***
-        MicroPython v1.24.0-preview.179.g5b85b24bd on 2024-08-05; zephyr-frdm_k64f with mk64f12
+        *** Booting Zephyr OS build v4.2.0 ***
+        MicroPython v1.26.0-preview.451.gebc9525c9 on 2025-07-25; zephyr-frdm_k64f with mk64f12
         Type "help()" for more information.
         >>>
 

ports/zephyr/README.md

@@ -5,8 +5,8 @@ This is a work-in-progress port of MicroPython to Zephyr RTOS
 (http://zephyrproject.org).
 
 This port tries to support all Zephyr versions supported upstream,
-i.e. currently v3.7 (LTS), v4.0 and the development branch. The CI is
-setup to use the latest version, i.e. v4.0.
+i.e. currently v3.7 (LTS), v4.2 and the development branch. The CI is
+setup to use the latest version, i.e. v4.2.
 
 All boards supported by Zephyr (with standard level of features
 support, like UART console) should work with MicroPython (but not all
@@ -43,13 +43,13 @@ setup is correct.
 If you already have Zephyr installed but are having issues building the
 MicroPython port then try installing the correct version of Zephyr via:
 
-    $ west init zephyrproject -m https://github.com/zephyrproject-rtos/zephyr --mr v4.0.0
+    $ west init zephyrproject -m https://github.com/zephyrproject-rtos/zephyr --mr v4.2.0
 
 Alternatively, you don't have to redo the Zephyr installation to just
 switch from master to a tagged release, you can instead do:
 
     $ cd zephyrproject/zephyr
-    $ git checkout v4.0.0
+    $ git checkout v4.2.0
     $ west update
 
 With Zephyr installed you may then need to configure your environment,

tools/ci.sh

@@ -886,9 +886,9 @@ function ci_windows_build {
 ########################################################################################
 # ports/zephyr
 
-ZEPHYR_DOCKER_VERSION=v0.27.4
-ZEPHYR_SDK_VERSION=0.17.0
-ZEPHYR_VERSION=v4.0.0
+ZEPHYR_DOCKER_VERSION=v0.28.1
+ZEPHYR_SDK_VERSION=0.17.2
+ZEPHYR_VERSION=v4.2.0
 
 function ci_zephyr_setup {
     IMAGE=ghcr.io/zephyrproject-rtos/ci:${ZEPHYR_DOCKER_VERSION}