ARM: dts: stm32: Add generic SoM compatible to STM32MP15xx DH electronics DHSOM

Add generic SoM compatible string into machine compatible string
for all STM32MP15xx based DH electronics DHSOM. This way, common
board code can match on this compatible. No functional change.

Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
diff --git a/arch/arm/dts/stm32mp15xx-dhcom-drc02.dts b/arch/arm/dts/stm32mp15xx-dhcom-drc02.dts
index 1ef9ac2..90625bf 100644
--- a/arch/arm/dts/stm32mp15xx-dhcom-drc02.dts
+++ b/arch/arm/dts/stm32mp15xx-dhcom-drc02.dts
@@ -11,5 +11,7 @@
 
 / {
 	model = "DH Electronics STM32MP15xx DHCOM DRC02";
-	compatible = "dh,stm32mp15xx-dhcom-drc02", "st,stm32mp1xx";
+	compatible = "dh,stm32mp15xx-dhcom-drc02",
+		     "dh,stm32mp15xx-dhcom-som",
+		     "st,stm32mp1xx";
 };