devicetree: Add documentation for UPISEMI us5182d ALS and Proximity sensor

* UPISEMI us5182d I2C ALS and Proximity sensor

Required properties:

- compatible: must be "upisemi,usd5182"

- reg: the I2C address of the device

Optional properties:

- upisemi,glass-coef: glass attenuation factor - compensation factor of

                      resolution 1000 for material transmittance.

- upisemi,dark-ths: array of 8 elements containing 16-bit thresholds (adc

                    counts) corresponding to every scale.

- upisemi,upper-dark-gain: 8-bit dark gain compensation factor(4 int and 4

                           fractional bits - Q4.4) applied when light > threshold

- upisemi,lower-dark-gain: 8-bit dark gain compensation factor(4 int and 4

                           fractional bits - Q4.4) applied when light < threshold

If the optional properties are not specified these factors will default to the

values in the below example.

The glass-coef defaults to no compensation for the covering material.

The threshold array defaults to experimental values that work with US5182D

sensor on evaluation board - roughly between 12-32 lux.

There will be no dark-gain compensation by default when ALS > thresh

(0 * dark-gain), and a 1.35 compensation factor when ALS < thresh.

Example:

    usd5182@39 {

                compatible = "upisemi,usd5182";

                reg = <0x39>;

                upisemi,glass-coef = < 1000 >;

                upisemi,dark-ths = /bits/ 16 <170 200 512 512 800 2000 4000 8000>;

                upisemi,upper-dark-gain = /bits/ 8 <0x00>;

                upisemi,lower-dark-gain = /bits/ 8 <0x16>;

    };

toumaz	Toumaz

tplink	TP-LINK Technologies Co., Ltd.

truly	Truly Semiconductors Limited

upisemi	uPI Semiconductor Corp.

usi	Universal Scientific Industrial Co., Ltd.

v3	V3 Semiconductor

variscite	Variscite Ltd.