diff --git a/Documentation/devicetree/bindings/media/cec-gpio.txt b/Documentation/devicetree/bindings/media/cec-gpio.txt
index 46a0bac8b3b9..12fcd55ed153 100644
--- a/Documentation/devicetree/bindings/media/cec-gpio.txt
+++ b/Documentation/devicetree/bindings/media/cec-gpio.txt
@@ -4,6 +4,10 @@ The HDMI CEC GPIO module supports CEC implementations where the CEC line
 is hooked up to a pull-up GPIO line and - optionally - the HPD line is
 hooked up to another GPIO line.
 
+Please note: the maximum voltage for the CEC line is 3.63V, for the HPD
+line it is 5.3V. So you may need some sort of level conversion circuitry
+when connecting them to a GPIO line.
+
 Required properties:
   - compatible: value must be "cec-gpio".
   - cec-gpios: gpio that the CEC line is connected to. The line should be
@@ -21,7 +25,7 @@ the following property is optional:
 
 Example for the Raspberry Pi 3 where the CEC line is connected to
 pin 26 aka BCM7 aka CE1 on the GPIO pin header and the HPD line is
-connected to pin 11 aka BCM17:
+connected to pin 11 aka BCM17 (some level shifter is needed for this!):
 
 #include <dt-bindings/gpio/gpio.h>