diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 244e8ff119777d1c9a237ae89209441fd9350c52..7aca22c9976d0f37a9d8f3e0b0cf6a41d6a3d787 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -2326,6 +2326,12 @@ static struct uart_driver serial8250_reg = {
 	.cons			= SERIAL8250_CONSOLE,
 };
 
+/*
+ * early_serial_setup - early registration for 8250 ports
+ *
+ * Setup an 8250 port structure prior to console initialisation.  Use
+ * after console initialisation will cause undefined behaviour.
+ */
 int __init early_serial_setup(struct uart_port *port)
 {
 	if (port->line >= ARRAY_SIZE(serial8250_ports))