dts: add a mention of issue in readme

Update the README with the related issue on u3 serie.

Signed-off-by: Fabrice DJIATSA <[email protected]>

Author: djiatsaf-st

dts/README.rst

@@ -43,4 +43,10 @@ License Link:
    https://www.apache.org/licenses/LICENSE-2.0
 
 Patch List:
-   None
+   *Missing additional pins for SAI1_FS_A and SAI1_FS_B signals on STM32U3 serie
+      - Add the SAI1_FS_A signal name on PB9 and PE4 in the appropriate U3 pinctrl file.
+      - Add the SAI1_FS_B signal name on PE9 in the appropriate U3 pinctrl files.
+      -Link: https://github.com/STMicroelectronics/STM32_open_pin_data/issues/15
+      - Impacted files:
+         dts/st/u3/stm32u375*-pinctrl.dtsi
+         dts/st/u3/stm32u385*-pinctrl.dtsi