arch/nrf53: add systimer configuration

arch/arm/src/nrf53/Kconfig

@@ -132,3 +132,34 @@ config NRF53_OSCILLATOR_LFXO
 		Configure LFXO oscillator
 
 endmenu # Clock Configuration
+
+menu "System Timer"
+
+config NRF53_SYSTIMER
+	bool
+	default y
+
+choice
+	prompt "System Timer Source"
+	default NRF53_SYSTIMER_SYSTICK
+	---help---
+		Choose which hardware resource will drive NuttX
+		system time
+
+config NRF53_SYSTIMER_SYSTICK
+	bool "SysTick"
+	select TIMER_ARCH
+	select TIMER
+	select ARMV8M_SYSTICK
+	---help---
+		Use ARM SysTick. It can be used for tickless and
+		non-tickless mode.
+
+		NOTE: nrf53 implementation of WFE/WFI involves is
+		incompatible with SysTick. This means that if
+		you choose this option, WFE/WFI will not be used
+		in idle loop.
+
+endchoice
+
+endmenu # System Timer

arch/arm/src/nrf53/Make.defs

@@ -20,7 +20,9 @@
 
 include armv8-m/Make.defs
 
+ifeq ($(CONFIG_NRF53_SYSTIMER_SYSTICK),y)
 CHIP_CSRCS += nrf53_systick.c
+endif
 CHIP_CSRCS += nrf53_start.c nrf53_clockconfig.c nrf53_irq.c nrf53_utils.c
 CHIP_CSRCS += nrf53_allocateheap.c nrf53_lowputc.c nrf53_gpio.c