diff --git a/drivers/tty/serial/8250/8250_of.c b/drivers/tty/serial/8250/8250_of.c
index 34f17a9785e7..9dcc17e33269 100644
--- a/drivers/tty/serial/8250/8250_of.c
+++ b/drivers/tty/serial/8250/8250_of.c
@@ -4,7 +4,10 @@
  *
  *    Copyright (C) 2006 Arnd Bergmann <arnd@arndb.de>, IBM Corp.
  */
+
+#include <linux/bits.h>
 #include <linux/console.h>
+#include <linux/math.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/serial_core.h>
@@ -25,6 +28,36 @@ struct of_serial_info {
 	int line;
 };
 
+/* Nuvoton NPCM timeout register */
+#define UART_NPCM_TOR          7
+#define UART_NPCM_TOIE         BIT(7)  /* Timeout Interrupt Enable */
+
+static int npcm_startup(struct uart_port *port)
+{
+	/*
+	 * Nuvoton calls the scratch register 'UART_TOR' (timeout
+	 * register). Enable it, and set TIOC (timeout interrupt
+	 * comparator) to be 0x20 for correct operation.
+	 */
+	serial_port_out(port, UART_NPCM_TOR, UART_NPCM_TOIE | 0x20);
+
+	return serial8250_do_startup(port);
+}
+
+/* Nuvoton NPCM UARTs have a custom divisor calculation */
+static unsigned int npcm_get_divisor(struct uart_port *port, unsigned int baud,
+				     unsigned int *frac)
+{
+	return DIV_ROUND_CLOSEST(port->uartclk, 16 * baud + 2) - 2;
+}
+
+static int npcm_setup(struct uart_port *port)
+{
+	port->get_divisor = npcm_get_divisor;
+	port->startup = npcm_startup;
+	return 0;
+}
+
 /*
  * Fill a struct uart_port for a given device node
  */
@@ -164,10 +197,17 @@ static int of_platform_serial_setup(struct platform_device *ofdev,
 	switch (type) {
 	case PORT_RT2880:
 		ret = rt288x_setup(port);
-		if (ret)
-			goto err_pmruntime;
+		break;
+	case PORT_NPCM:
+		ret = npcm_setup(port);
+		break;
+	default:
+		/* Nothing to do */
+		ret = 0;
 		break;
 	}
+	if (ret)
+		goto err_pmruntime;
 
 	if (IS_REACHABLE(CONFIG_SERIAL_8250_FSL) &&
 	    (of_device_is_compatible(np, "fsl,ns16550") ||
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 1d65055dde27..c0c34e410c58 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -38,10 +38,6 @@
 
 #include "8250.h"
 
-/* Nuvoton NPCM timeout register */
-#define UART_NPCM_TOR          7
-#define UART_NPCM_TOIE         BIT(7)  /* Timeout Interrupt Enable */
-
 /*
  * Debugging.
  */
@@ -2229,15 +2225,6 @@ int serial8250_do_startup(struct uart_port *port)
 				UART_DA830_PWREMU_MGMT_FREE);
 	}
 
-	if (port->type == PORT_NPCM) {
-		/*
-		 * Nuvoton calls the scratch register 'UART_TOR' (timeout
-		 * register). Enable it, and set TIOC (timeout interrupt
-		 * comparator) to be 0x20 for correct operation.
-		 */
-		serial_port_out(port, UART_NPCM_TOR, UART_NPCM_TOIE | 0x20);
-	}
-
 #ifdef CONFIG_SERIAL_8250_RSA
 	/*
 	 * If this is an RSA port, see if we can kick it up to the
@@ -2539,15 +2526,6 @@ static void serial8250_shutdown(struct uart_port *port)
 		serial8250_do_shutdown(port);
 }
 
-/* Nuvoton NPCM UARTs have a custom divisor calculation */
-static unsigned int npcm_get_divisor(struct uart_8250_port *up,
-		unsigned int baud)
-{
-	struct uart_port *port = &up->port;
-
-	return DIV_ROUND_CLOSEST(port->uartclk, 16 * baud + 2) - 2;
-}
-
 static unsigned int serial8250_do_get_divisor(struct uart_port *port,
 					      unsigned int baud,
 					      unsigned int *frac)
@@ -2592,8 +2570,6 @@ static unsigned int serial8250_do_get_divisor(struct uart_port *port,
 		quot = 0x8001;
 	else if (magic_multiplier && baud >= port->uartclk / 12)
 		quot = 0x8002;
-	else if (up->port.type == PORT_NPCM)
-		quot = npcm_get_divisor(up, baud);
 	else
 		quot = uart_get_divisor(port, baud);