dt-bindings: battery: add new battery parameters

Add:

 - trickle-charge-current-microamp:

Some chargers have 3 charging stages. First one when battery is almost
empty is often called as trickle-charge. Last state when battery has been
"woken up" is usually called as fast-charge. In addition to this some
chargers have a 'middle state' which ROHM BD99954 data-sheet describes as
pre-charge. Some batteries can benefit from this 3-phase charging
[citation needed].

Introduce trickle-charge-current-microamp so that batteries can give
charging current limit for all three states.

 - precharge-upper-limit-microvolt:

When battery voltage has reached certain limit we change from
trickle-charge to next charging state (pre-charge for BD99954). Allow
battery to specify this limit.

 - re-charge-voltage-microvolt:

Allow giving a battery specific voltage limit for chargers which can
automatically re-start charging when battery has discharghed down to
this limit.

- over-voltage-threshold-microvolt

Allow specifying voltage threshold after which the battery is assumed to
be faulty.
Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

Documentation/devicetree/bindings/power/supply/battery.txt

@@ -11,15 +11,21 @@ different type. This prevents unpredictable, potentially harmful,
 behavior should a replacement that changes the battery type occur
 without a corresponding update to the dtb.
 
+Please note that not all charger drivers respect all of the properties.
+
 Required Properties:
  - compatible: Must be "simple-battery"
 
 Optional Properties:
+ - over-voltage-threshold-microvolt: battery over-voltage limit
+ - re-charge-voltage-microvolt: limit to automatically start charging again
  - voltage-min-design-microvolt: drained battery voltage
  - voltage-max-design-microvolt: fully charged battery voltage
  - energy-full-design-microwatt-hours: battery design energy
  - charge-full-design-microamp-hours: battery design capacity
+ - trickle-charge-current-microamp: current for trickle-charge phase
  - precharge-current-microamp: current for pre-charge phase
+ - precharge-upper-limit-microvolt: limit when to change to constant charging
  - charge-term-current-microamp: current for charge termination phase
  - constant-charge-current-max-microamp: maximum constant input current
  - constant-charge-voltage-max-microvolt: maximum constant input voltage