You are on the wrong path. You need to fork the device and kernel files, modify them and put the path of your fork into the xml file. Take a look at 5.4 in the HADK.
<?xml version="1.0" encoding="UTF-8"?> <manifest> <project path="device/lge/hammerhead" name="edp17/android_device_lge_hammerhead" revision="stable/cm-12.1-YOG4P" /> <project path="kernel/lge/hammerhead" name="edp17/android_kernel_lge_hammerhead" revision="stable/cm-12.1-YOG4P" /> <project path="hybris/droid-hal-version-hammerhead" name="edp17/droid-hal-version-hammerhead-12.1" revision="master" /> <project path="hybris/droid-configs" name="edp17/droid-config-hammerhead-12.1" revision="master" /> <project path="rpm" name="edp17/droid-hal-hammerhead-12.1" revision="master" /> <project path="vendor/lge" name="edp17/proprietary_vendor_lge" revision="stable/cm-12.1-YOG4P" /> </manifest>