see Documentation/devicetree/bindings/leds/common.txt
- retain-state-suspended: (optional) The suspend state can be retained.Such
as charge-led gpio.
+- retain-state-shutdown: (optional) Retain the state of the LED on shutdown.
+ Useful in BMC systems, for example when the BMC is rebooted while the host
+ remains up.
- panic-indicator : (optional)
see Documentation/devicetree/bindings/leds/common.txt