diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
index 70d7826788f5..c171ce6db691 100644
--- a/drivers/tty/serial/8250/8250_early.c
+++ b/drivers/tty/serial/8250/8250_early.c
@@ -204,9 +204,6 @@ OF_EARLYCON_DECLARE(omap8250, "ti,omap4-uart", early_omap8250_setup);
 
 #ifdef CONFIG_SERIAL_8250_RT288X
 
-unsigned int au_serial_in(struct uart_port *p, int offset);
-void au_serial_out(struct uart_port *p, int offset, int value);
-
 static int __init early_au_setup(struct earlycon_device *dev, const char *opt)
 {
 	dev->port.serial_in = au_serial_in;
diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
index 2b70f736b091..9e655055112d 100644
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h
@@ -187,4 +187,9 @@ extern void serial8250_set_isa_configurator(void (*v)
 					(int port, struct uart_port *up,
 						u32 *capabilities));
 
+#ifdef CONFIG_SERIAL_8250_RT288X
+unsigned int au_serial_in(struct uart_port *p, int offset);
+void au_serial_out(struct uart_port *p, int offset, int value);
+#endif
+
 #endif