dt-bindings: i2c: designware: document MSCC Ocelot bindings

Document bindings for the Microsemi Ocelot integration of the Designware
I2C controller.
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-designware.txt

@@ -3,6 +3,7 @@
 Required properties :
 
  - compatible : should be "snps,designware-i2c"
+                or "mscc,ocelot-i2c" with "snps,designware-i2c" for fallback
  - reg : Offset and length of the register set for the device
  - interrupts : <IRQ> where IRQ is the interrupt number.
 
@@ -11,8 +12,12 @@ Recommended properties :
  - clock-frequency : desired I2C bus clock frequency in Hz.
 
 Optional properties :
+ - reg : for "mscc,ocelot-i2c", a second register set to configure the SDA hold
+   time, named ICPU_CFG:TWI_DELAY in the datasheet.
+
  - i2c-sda-hold-time-ns : should contain the SDA hold time in nanoseconds.
-   This option is only supported in hardware blocks version 1.11a or newer.
+   This option is only supported in hardware blocks version 1.11a or newer and
+   on Microsemi SoCs ("mscc,ocelot-i2c" compatible).
 
  - i2c-scl-falling-time-ns : should contain the SCL falling time in nanoseconds.
    This value which is by default 300ns is used to compute the tLOW period.