fng-install:rtc: Added device check to RTC post-install

Added a check to the RTC post-install script, that detects if the device is a Tanaro. If it is not, the check exits the script.

Cherry-picked from 247db5f3 and 3b84b29d

recipes-bsp/fng-install/prepare-image/gf-prepare-rtc.sh

@@ -10,15 +10,22 @@ if ! . /usr/sbin/gf-prepare-common.sh; then
 fi
 
 poll_rtc() {
+    # Check if there is an I2C device at the know bus and address.
+    # If the tool returns 'Device or resource busy' we assume a
+    # driver has grabed the existing RTC device.
     if i2cget -y 2 "$1" 0x00 2>&1 | grep -E '.*0x.*|.*Device or resource busy.*'; then
-        echo "Device found at address $1"
         return 0
     else
-        echo "No device found at address $1"
         return 1
     fi
 }
 
+# The RTC detection only applies to the Tanaro at the moment.
+if ! grep -q -i Tanaro /sys/devices/soc0/machine; then
+    echo "The device is not a 'Tanaro'; Skipping the RTC detection ..."
+    exit 0
+fi
+
 # Get the directory containing the bootfiles
 mount_bootpartition BOOTFILES_DIR
 
@@ -27,13 +34,15 @@ cd "$BOOTFILES_DIR" || exit 1
 
 # RX8803
 if poll_rtc 0x32; then
+    echo "Selecting overlay 'rx8803-overlay.dtb'"
     append_overlay "rx8803-overlay.dtb"
 else
     # PCF8563
     if poll_rtc 0x51; then
+        echo "Selecting overlay 'pcf8563-overlay.dtb'"
         append_overlay "pcf8563-overlay.dtb"
     else
-        echo "Error: Unable to find any valid device"
+        echo "Error: Unable to find any valid RTC device, not applying any overlay."
         exit 1
     fi
 fi