kernel: idle: introduce idle enter hook

include/zephyr/platform/hooks.h

@@ -78,4 +78,12 @@ void board_early_init_hook(void);
  */
 void board_late_init_hook(void);
 
+/**
+ * @brief Hook executed when idle is entered.
+ *
+ * This hook is implemented by the SoC and can be used to perform any
+ * SoC-specific idle enter logic.
+ */
+void idle_enter_hook(void);
+
 #endif

kernel/Kconfig

@@ -1078,3 +1078,4 @@ endmenu
 rsource "Kconfig.device"
 rsource "Kconfig.vm"
 rsource "Kconfig.init"
+rsource "Kconfig.idle"

kernel/Kconfig.idle

@@ -0,0 +1,15 @@
+# Copyright (c) 2025 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+menu "Kernel idle options"
+
+config IDLE_ENTER_HOOK
+	bool "Execute idle enter hook"
+	help
+	  Execute idle_exit_hook() when entering idle.
+
+config IDLE_DEFAULT_ROUTINE
+	bool "Execute idle default routine"
+	default y
+
+endmenu

kernel/idle.c

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2016 Wind River Systems, Inc.
+ * Copyright (c) 2025 Nordic Semiconductor ASA
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -27,6 +28,11 @@ void idle(void *unused1, void *unused2, void *unused3)
 	__ASSERT_NO_MSG(arch_current_thread()->base.prio >= 0);
 
 	while (true) {
+#ifdef CONFIG_IDLE_ENTER_HOOK
+		idle_enter_hook();
+#endif /* CONFIG_IDLE_ENTER_HOOK */
+
+#ifdef CONFIG_IDLE_DEFAULT_ROUTINE
 		/* SMP systems without a working IPI can't actual
 		 * enter an idle state, because they can't be notified
 		 * of scheduler changes (i.e. threads they should
@@ -90,6 +96,7 @@ void idle(void *unused1, void *unused2, void *unused3)
 		}
 # endif /* !defined(CONFIG_USE_SWITCH) || defined(CONFIG_SPARC) */
 #endif /* !defined(CONFIG_PREEMPT_ENABLED) */
+#endif /* CONFIG_IDLE_DEFAULT_ROUTINE */
 	}
 }