nrf: Add support to activate MICROPY_PY_SYS_STDFILES.

Fixes issue #5162.

ports/nrf/Makefile

@@ -156,6 +156,7 @@ SRC_LIB += $(addprefix lib/,\
 	libc/string0.c \
 	mp-readline/readline.c \
 	utils/pyexec.c \
+	utils/sys_stdio_mphal.c \
 	utils/interrupt_char.c \
 	timeutils/timeutils.c \
 	)
@@ -342,7 +343,7 @@ $(BUILD)/$(OUTPUT_FILENAME).elf: $(OBJ)
 	$(Q)$(SIZE) $@
 
 # List of sources for qstr extraction
-SRC_QSTR += $(SRC_C) $(DRIVERS_SRC_C) $(SRC_BOARD_MODULES)
+SRC_QSTR += $(SRC_C) $(SRC_LIB) $(DRIVERS_SRC_C) $(SRC_BOARD_MODULES)
 
 # Append any auto-generated sources that are needed by sources listed in
 # SRC_QSTR

ports/nrf/mphalport.c

@@ -30,6 +30,7 @@
 #include "py/mphal.h"
 #include "py/mperrno.h"
 #include "py/runtime.h"
+#include "py/stream.h"
 #include "uart.h"
 #include "nrfx_errors.h"
 #include "nrfx_config.h"
@@ -53,6 +54,15 @@ void mp_hal_set_interrupt_char(int c) {
 #endif
 
 #if !MICROPY_PY_BLE_NUS
+uintptr_t mp_hal_stdio_poll(uintptr_t poll_flags) {
+    uintptr_t ret = 0;
+    if ((poll_flags & MP_STREAM_POLL_RD) && MP_STATE_PORT(board_stdio_uart) != NULL
+        && uart_rx_any(MP_STATE_PORT(board_stdio_uart))) {
+        ret |= MP_STREAM_POLL_RD;
+    }
+    return ret;
+}
+
 int mp_hal_stdin_rx_chr(void) {
     for (;;) {
         if (MP_STATE_PORT(board_stdio_uart) != NULL && uart_rx_any(MP_STATE_PORT(board_stdio_uart))) {