net: openthread: implement `otPlatRadioGetCslUncertainty`

Implement the OpenThread API to retrieve the platforms CSL
Uncertainty.

Signed-off-by: Eduardo Montoya <eduardo.montoya@nordicsemi.no>
diff --git a/subsys/net/l2/openthread/Kconfig.thread b/subsys/net/l2/openthread/Kconfig.thread
index f7a0967..6f0b111 100644
--- a/subsys/net/l2/openthread/Kconfig.thread
+++ b/subsys/net/l2/openthread/Kconfig.thread
@@ -97,10 +97,11 @@
 	  The minimum CSL receive window (in microseconds) required to receive a full IEEE 802.15.4 frame
 
 config OPENTHREAD_PLATFORM_CSL_UNCERT
-	int "CSL clock uncertainty"
+	int "CSL uncertainty"
 	default 255
+	range 0 255
 	help
-	  The Uncertainty of the scheduling CSL of transmission by the parent, in ±10 us units.
+	  The fixed uncertainty of the Device for scheduling CSL Transmissions in units of 10 microseconds.
 
 config OPENTHREAD_MAC_SOFTWARE_TX_SECURITY_ENABLE
 	bool "Software transmission security logic"
diff --git a/subsys/net/lib/openthread/platform/openthread-core-zephyr-config.h b/subsys/net/lib/openthread/platform/openthread-core-zephyr-config.h
index 7f289f2..90234f2 100644
--- a/subsys/net/lib/openthread/platform/openthread-core-zephyr-config.h
+++ b/subsys/net/lib/openthread/platform/openthread-core-zephyr-config.h
@@ -317,16 +317,6 @@
 #endif /* CONFIG_OPENTHREAD_CSL_MIN_RECEIVE_ON */
 
 /**
- * @def OPENTHREAD_CONFIG_PLATFORM_CSL_UNCERT
- *
- * The Uncertainty of the scheduling CSL of transmission by the parent, in ±10 us units.
- */
-
-#ifdef CONFIG_OPENTHREAD_PLATFORM_CSL_UNCERT
-#define OPENTHREAD_CONFIG_PLATFORM_CSL_UNCERT CONFIG_OPENTHREAD_PLATFORM_CSL_UNCERT
-#endif /* CONFIG_OPENTHREAD_PLATFORM_CSL_UNCERT */
-
-/**
  * @def OPENTHREAD_CONFIG_MAC_SOFTWARE_TX_SECURITY_ENABLE
  *
  * Set to 1 to enable software transmission security logic.
diff --git a/subsys/net/lib/openthread/platform/radio.c b/subsys/net/lib/openthread/platform/radio.c
index bdc792b..2601b70 100644
--- a/subsys/net/lib/openthread/platform/radio.c
+++ b/subsys/net/lib/openthread/platform/radio.c
@@ -1135,6 +1135,15 @@
 	return radio_api->get_sch_acc(radio_dev);
 }
 
+#if defined(CONFIG_OPENTHREAD_PLATFORM_CSL_UNCERT)
+uint8_t otPlatRadioGetCslUncertainty(otInstance *aInstance)
+{
+	ARG_UNUSED(aInstance);
+
+	return CONFIG_OPENTHREAD_PLATFORM_CSL_UNCERT;
+}
+#endif
+
 #if defined(CONFIG_OPENTHREAD_LINK_METRICS_SUBJECT)
 /**
  * Header IE format - IEEE Std. 802.15.4-2015, 7.4.2.1 && 7.4.2.2