diff --git a/arch/arm/soc/nxp_kinetis/k6x/soc.h b/arch/arm/soc/nxp_kinetis/k6x/soc.h
index 7ec7b16c183..61fb2247055 100644
--- a/arch/arm/soc/nxp_kinetis/k6x/soc.h
+++ b/arch/arm/soc/nxp_kinetis/k6x/soc.h
@@ -34,6 +34,8 @@ extern "C" {
 /* default system clock */
 
 #define SYSCLK_DEFAULT_IOSC_HZ MHZ(120)
+#define BUSCLK_DEFAULT_IOSC_HZ (SYSCLK_DEFAULT_IOSC_HZ / \
+				CONFIG_K64_BUS_CLOCK_DIVIDER)
 
 /* address bases */
 
@@ -153,22 +155,25 @@ extern "C" {
 
 #include <drivers/k20_pcr.h>
 
-#define UART_K20_CLK_FREQ		SYSCLK_DEFAULT_IOSC_HZ
-
 #define UART_IRQ_FLAGS 0
 
+#define UART_K20_PORT_0_CLK_FREQ	SYSCLK_DEFAULT_IOSC_HZ
 #define UART_K20_PORT_0_BASE_ADDR	0x4006A000
 #define UART_K20_PORT_0_IRQ		IRQ_UART0_STATUS
 
+#define UART_K20_PORT_1_CLK_FREQ	SYSCLK_DEFAULT_IOSC_HZ
 #define UART_K20_PORT_1_BASE_ADDR	0x4006B000
 #define UART_K20_PORT_1_IRQ		IRQ_UART1_STATUS
 
+#define UART_K20_PORT_2_CLK_FREQ	BUSCLK_DEFAULT_IOSC_HZ
 #define UART_K20_PORT_2_BASE_ADDR	0x4006C000
 #define UART_K20_PORT_2_IRQ		IRQ_UART2_STATUS
 
+#define UART_K20_PORT_3_CLK_FREQ	BUSCLK_DEFAULT_IOSC_HZ
 #define UART_K20_PORT_3_BASE_ADDR	0x4006D000
 #define UART_K20_PORT_3_IRQ		IRQ_UART3_STATUS
 
+#define UART_K20_PORT_4_CLK_FREQ	BUSCLK_DEFAULT_IOSC_HZ
 #define UART_K20_PORT_4_BASE_ADDR	0x400EA000
 #define UART_K20_PORT_4_IRQ		IRQ_UART4_STATUS
 
diff --git a/drivers/serial/uart_k20.c b/drivers/serial/uart_k20.c
index 86c5ea62669..710665bf17d 100644
--- a/drivers/serial/uart_k20.c
+++ b/drivers/serial/uart_k20.c
@@ -416,7 +416,7 @@ static void irq_config_func_0(struct device *port);
 
 static const struct uart_device_config uart_k20_dev_cfg_0 = {
 	.base = (uint8_t *)UART_K20_PORT_0_BASE_ADDR,
-	.sys_clk_freq = UART_K20_CLK_FREQ,
+	.sys_clk_freq = UART_K20_PORT_0_CLK_FREQ,
 
 #ifdef CONFIG_UART_INTERRUPT_DRIVEN
 	.irq_config_func = irq_config_func_0,
@@ -453,7 +453,7 @@ static void irq_config_func_1(struct device *port);
 
 static const struct uart_device_config uart_k20_dev_cfg_1 = {
 	.base = (uint8_t *)UART_K20_PORT_1_BASE_ADDR,
-	.sys_clk_freq = UART_K20_CLK_FREQ,
+	.sys_clk_freq = UART_K20_PORT_1_CLK_FREQ,
 
 #ifdef CONFIG_UART_INTERRUPT_DRIVEN
 	.irq_config_func = irq_config_func_1,
@@ -490,7 +490,7 @@ static void irq_config_func_2(struct device *port);
 
 static const struct uart_device_config uart_k20_dev_cfg_2 = {
 	.base = (uint8_t *)UART_K20_PORT_2_BASE_ADDR,
-	.sys_clk_freq = UART_K20_CLK_FREQ,
+	.sys_clk_freq = UART_K20_PORT_2_CLK_FREQ,
 
 #ifdef CONFIG_UART_INTERRUPT_DRIVEN
 	.irq_config_func = irq_config_func_2,
@@ -527,7 +527,7 @@ static void irq_config_func_3(struct device *port);
 
 static struct uart_device_config uart_k20_dev_cfg_3 = {
 	.base = (uint8_t *)UART_K20_PORT_3_BASE_ADDR,
-	.sys_clk_freq = UART_K20_CLK_FREQ,
+	.sys_clk_freq = UART_K20_PORT_3_CLK_FREQ,
 
 #ifdef CONFIG_UART_INTERRUPT_DRIVEN
 	.irq_config_func = irq_config_func_3,
@@ -564,7 +564,7 @@ static void irq_config_func_4(struct device *port);
 
 static const struct uart_device_config uart_k20_dev_cfg_4 = {
 	.base = (uint8_t *)UART_K20_PORT_4_BASE_ADDR,
-	.sys_clk_freq = UART_K20_CLK_FREQ,
+	.sys_clk_freq = UART_K20_PORT_4_CLK_FREQ,
 
 #ifdef CONFIG_UART_INTERRUPT_DRIVEN
 	.irq_config_func = irq_config_func_4,