powerpc/microwatt: Populate platform bus from device-tree

Just like any other embedded platform.

Add an empty soc node.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/YMwWx98+PMibZq/G@thinks.paulus.ozlabs.org

arch/powerpc/boot/dts/microwatt.dts

@@ -95,4 +95,11 @@ chosen {
 					  00 00 00 00 00 00 00 00 40 00 40];
 	};
 
+	soc@c0000000 {
+		compatible = "simple-bus";
+		#address-cells = <1>;
+		#size-cells = <1>;
+
+		ranges = <0 0 0xc0000000 0x40000000>;
+	};
 };

arch/powerpc/platforms/microwatt/setup.c

@@ -8,6 +8,8 @@
 #include <linux/kernel.h>
 #include <linux/stddef.h>
 #include <linux/init.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
 #include <asm/machdep.h>
 #include <asm/time.h>
 
@@ -16,6 +18,12 @@ static int __init microwatt_probe(void)
 	return of_machine_is_compatible("microwatt-soc");
 }
 
+static int __init microwatt_populate(void)
+{
+	return of_platform_default_populate(NULL, NULL, NULL);
+}
+machine_arch_initcall(microwatt, microwatt_populate);
+
 define_machine(microwatt) {
 	.name			= "microwatt",
 	.probe			= microwatt_probe,