doc: releases: migration-guide: add nRF53 L|HFXO changes

Infom users about Kconfig options deprecation, and provide code snippets
on what they have to do now.

(cherry picked from commit 4b2c030)

Original-Signed-off-by: Gerard Marull-Paretas <gerard@teslabs.com>
GitOrigin-RevId: 4b2c030
Cr-Build-Id: 8736283099024849217
Cr-Build-Url: https://cr-buildbucket.appspot.com/build/8736283099024849217
Copybot-Job-Name: zephyr-main-copybot-downstream
Change-Id: Ia5b2ef62b29906c7dceb962fc44ad66ce1cfc458
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/zephyr/+/5878226
Tested-by: Tristan Honscheid <honscheid@google.com>
Reviewed-by: Tristan Honscheid <honscheid@google.com>
Tested-by: ChromeOS Prod (Robot) <chromeos-ci-prod@chromeos-bot.iam.gserviceaccount.com>
Commit-Queue: Tristan Honscheid <honscheid@google.com>

doc/releases/migration-guide-4.0.rst

@@ -102,6 +102,53 @@ Device Drivers and Devicetree
   their driver API, users of these devices should ensure they pass appropriate values to
   :c:func:`gpio_pin_set`. (:github:`65797`)
 
+Clock control
+=============
+
+* LFXO/HFXO (High/Low Frequency Crystal Oscillator) present in nRF53 series can
+  now be configured using devicetree. The Kconfig options
+  :kconfig:option:`CONFIG_SOC_ENABLE_LFXO`,
+  :kconfig:option:`CONFIG_SOC_LFXO_CAP_EXTERNAL`,
+  :kconfig:option:`CONFIG_SOC_LFXO_CAP_INT_6PF`,
+  :kconfig:option:`CONFIG_SOC_LFXO_CAP_INT_7PF`,
+  :kconfig:option:`CONFIG_SOC_LFXO_CAP_INT_9PF`,
+  :kconfig:option:`CONFIG_SOC_HFXO_CAP_DEFAULT`,
+  :kconfig:option:`CONFIG_SOC_HFXO_CAP_EXTERNAL`,
+  :kconfig:option:`CONFIG_SOC_HFXO_CAP_INTERNAL` and
+  :kconfig:option:`CONFIG_SOC_HFXO_CAP_INT_VALUE_X2` have been deprecated.
+
+  LFXO can now be configured like this:
+
+  .. code-block:: devicetree
+
+     /* use external capacitors */
+     &lfxo {
+           load-capacitors = "external";
+     };
+
+     /* use internal capacitors (value needs to be selected: 6, 7, 9pF)
+     &lfxo {
+           load-capacitors = "internal";
+           load-capacitance-picofarad = <...>;
+     };
+
+  HFXO can now be configured like this:
+
+  .. code-block:: devicetree
+
+     /* use external capacitors */
+     &hfxo {
+           load-capacitors = "external";
+     };
+
+     /* use internal capacitors (value needs to be selected: 7pF...20pF in 0.5pF
+      * steps, units: femtofarads)
+      */
+     &hfxo {
+           load-capacitors = "internal";
+           load-capacitance-femtofarad = <...>;
+     };
+
 Controller Area Network (CAN)
 =============================