dt-bindings: i2c-stm32: Document the STM32F7 I2C bindings

This patch adds the documentation of device tree bindings for STM32F7 I2C
Signed-off-by: M'boumba Cedric Madianga <cedric.madianga@gmail.com>
Signed-off-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-stm32.txt

 * I2C controller embedded in STMicroelectronics STM32 I2C platform
 
 Required properties :
-- compatible : Must be "st,stm32f4-i2c"
+- compatible : Must be one of the following
+  - "st,stm32f4-i2c"
+  - "st,stm32f7-i2c"
 - reg : Offset and length of the register set for the device
 - interrupts : Must contain the interrupt id for I2C event and then the
   interrupt id for I2C error.
@@ -14,8 +16,16 @@ Required properties :
 
 Optional properties :
 - clock-frequency : Desired I2C bus clock frequency in Hz. If not specified,
-  the default 100 kHz frequency will be used. As only Normal and Fast modes
-  are supported, possible values are 100000 and 400000.
+  the default 100 kHz frequency will be used.
+  For STM32F4 SoC Standard-mode and Fast-mode are supported, possible values are
+  100000 and 400000.
+  For STM32F7 SoC, Standard-mode, Fast-mode and Fast-mode Plus are supported,
+  possible values are 100000, 400000 and 1000000.
+- i2c-scl-rising-time-ns : Only for STM32F7, I2C SCL Rising time for the board
+  (default: 25)
+- i2c-scl-falling-time-ns : Only for STM32F7, I2C SCL Falling time for the board
+  (default: 10)
+  I2C Timings are derived from these 2 values
 
 Example :
 
@@ -31,3 +41,16 @@ Example :
 		pinctrl-0 = <&i2c1_sda_pin>, <&i2c1_scl_pin>;
 		pinctrl-names = "default";
 	};
+
+	i2c@40005400 {
+		compatible = "st,stm32f7-i2c";
+		#address-cells = <1>;
+		#size-cells = <0>;
+		reg = <0x40005400 0x400>;
+		interrupts = <31>,
+			     <32>;
+		resets = <&rcc STM32F7_APB1_RESET(I2C1)>;
+		clocks = <&rcc 1 CLK_I2C1>;
+		pinctrl-0 = <&i2c1_sda_pin>, <&i2c1_scl_pin>;
+		pinctrl-names = "default";
+	};