dts: bindings: Add optional timings capability

By default the I2C timing (I2C_TIMINGR register) of I2C V2 peripheral is
computed depending on clocks at runtime with relatively low precision.

This optional property allows to provide a list of pre-computed values
(typically computed from STM32CubeMX SW tool) instead of using runtime
algorithm.

The precomputed value is only valid for a given clock configuration and
I2C speed setting, so this valid configuration is provided with each
value entry.

Signed-off-by: Laurent Meunier <laurent.meunier@st.com>

dts/bindings/i2c/st,stm32-i2c-v2.yaml

@@ -13,3 +13,28 @@ properties:
 
     interrupts:
       required: true
+
+    timings:
+        type: array
+        required: false
+        description: |
+            An optional table of pre-computed i2c timing values with the
+            matching clock configuration.
+
+            Precise timings values for a given Hardware can be pre-computed
+            with a tool like STM32CubeMX or directly from I2C_TIMINGR register
+            description.
+
+            Because timing value is valid for a given I2C peripheral clock
+            frequency and target I2C bus clock, each timing value must be
+            provided with the matching configuration.
+
+            The resulting table entries should look like <periph_clock
+            clock-frequency timing>
+
+            For example timings could be defined as
+
+                timings = <64000000 I2C_BITRATE_STANDARD 0x10707DBC>,
+                          <64000000 I2C_BITRATE_FAST 0x00603D56>,
+                          <56000000 I2C_BITRATE_STANDARD 0x10606DA4>,
+                          <56000000 I2C_BITRATE_FAST 0x00501D63>;