* I2C controller embedded in STMicroelectronics STM32 I2C platform

Required properties :
- 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.
- resets: Must contain the phandle to the reset controller.
- clocks: Must contain the input clock of the I2C instance.
- A pinctrl state named "default" must be defined to set pins in mode of
  operation for I2C transfer
- #address-cells = <1>;
- #size-cells = <0>;

Optional properties :
- clock-frequency : Desired I2C bus clock frequency in Hz. If not specified,
  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 :

	i2c@40005400 {
		compatible = "st,stm32f4-i2c";
		#address-cells = <1>;
		#size-cells = <0>;
		reg = <0x40005400 0x400>;
		interrupts = <31>,
			     <32>;
		resets = <&rcc 277>;
		clocks = <&rcc 0 149>;
		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";
	};