[arch][arm-m] add generic header/footer for arm-m handlers

arch/arm/arm-m/arch.c

@@ -24,6 +24,7 @@
 #include <arch.h>
 #include <arch/ops.h>
 #include <arch/arm.h>
+#include <kernel/thread.h>
 #include <platform.h>
 #include <arch/arm/cm.h>
 
@@ -121,3 +122,18 @@ void _arm_cm_set_irqpri(uint32_t pri)
 	}
 }
 
+void arm_cm_irq_entry(void)
+{
+	inc_critical_section();
+
+	THREAD_STATS_INC(interrupts);
+}
+
+void arm_cm_irq_exit(bool reschedule)
+{
+	if (reschedule)
+		arm_cm_trigger_preempt();
+
+	dec_critical_section();
+}
+

arch/arm/arm-m/include/arch/arm/cm.h

@@ -165,5 +165,13 @@ void arm_cm_systick_set_periodic(uint32_t systick_clk_freq, lk_time_t period);
 void arm_cm_systick_cancel_periodic(void);
 /* extern void _systick(void); // override this */
 
+/* interrupt glue */
+/*
+ * Platform code should put this as the first and last line of their irq handlers.
+ * Pass true to reschedule to request a preempt.
+ */
+void arm_cm_irq_entry(void);
+void arm_cm_irq_exit(bool reschedule);
+
 #endif