dm: Add dm_scan_other() to locate board-specific devices

Some boards will have devices which are not in the device tree and do not
have platform data. They may be programnatically created, for example.
Add a hook which boards can use to bind those devices early in boot.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/core/root.c

@@ -108,6 +108,11 @@ int dm_scan_fdt(const void *blob, bool pre_reloc_only)
 }
 #endif
 
+__weak int dm_scan_other(bool pre_reloc_only)
+{
+	return 0;
+}
+
 int dm_init_and_scan(bool pre_reloc_only)
 {
 	int ret;
@@ -129,6 +134,9 @@ int dm_init_and_scan(bool pre_reloc_only)
 		return ret;
 	}
 #endif
+	ret = dm_scan_other(pre_reloc_only);
+	if (ret)
+		return ret;
 
 	return 0;
 }