schemas: core: Introduce "fail-needs-probe" status

Some components can not be absolutely determined to exist on a given
device when the device tree is written or compiled. However such
components can either be probed using I2C transfers, or determined to
exist based on runtime information, such as GPIO or ADC strappings, or
extra information passed over from boot firmware or read from some
flash chip.

Such an arrangement of components are commonly seen in the
consumer electronics world, where the manufacturer will swap out
electrically compatible components due to inventory or price
constraints. These components are commonly attached to the baseboard
with a standardized ribbon cable, and the ribbon cable may contain
strapping resistors if necessary.

Introduce a new "fail-needs-probe" status string that corresponds to
devices or components that "might" exist. (The term "component" shall
be used to avoid confusion with the actual "complete device".) This
status signals that the implementation needs to do extra probing to
determine the exact state of the component.

Signed-off-by: Chen-Yu Tsai <[email protected]>

dtschema/schemas/dt-core.yaml

@@ -56,7 +56,7 @@ properties:
     oneOf:
       - type: object
       - $ref: types.yaml#/definitions/string
-        enum: [ okay, disabled, reserved, fail ]
+        enum: [ okay, disabled, reserved, fail, fail-needs-probe ]
   phandle:
     $ref: types.yaml#/definitions/uint32