Support U_BOOT_SEPARATE_BOOT configuration

etc/default/u-boot

@@ -10,6 +10,7 @@
 #U_BOOT_PARAMETERS="ro quiet"
 #U_BOOT_ROOT=""
 #U_BOOT_TIMEOUT="50"
+#U_BOOT_SEPARATE_BOOT="true"
 #U_BOOT_FDT=""
 #U_BOOT_FDT_DIR="/usr/lib/linux-image-"
 #U_BOOT_FDT_OVERLAYS=""

read-config

@@ -1,7 +1,11 @@
 #!/bin/sh
 
 has_separate_boot() {
-    [ "$(stat --printf %d /)" != "$(stat --printf %d /boot)" ]
+	if [ -z "${U_BOOT_SEPARATE_BOOT}" ]; then
+		[ "$(stat --printf %d /)" != "$(stat --printf %d /boot)" ]
+	else
+		"${U_BOOT_SEPARATE_BOOT}"
+	fi
 }
 
 # Reading the default file

u-boot-update.8

@@ -108,6 +108,15 @@ Values are in decisecond greater than 0
 0 specifies to wait forever.
 The default is 50.
 
+.IP "U_BOOT_SEPARATE_BOOT=""\fB50\fR""" 4
+This variable force setting the /boot detection result.
+This is helpful when constructing bootable disk images.
+Values are bool type if set,
+true specifies that /boot will be mounted separately,
+false specifies that /boot is stored inside /,
+unset the variable to enable auto detection.
+Unset by default.
+
 .IP "U_BOOT_FDT_DIR=""\fB/usr/lib/linux-image-\fR""" 4
 This variable specifies the unversioned stem of paths
 where U\-BOOT should look for the flattened device tree binaries.