Editing Device tree DTSI file

I have driver code for some hardware I am using . I need to assign it in device tree structure in kernel of mediatek X20. I dont want to use SPI_DEV to do it. How can I do it?
I tried editing in kernel-3.18/arch/arm64/boot/dts/mt6797.dtsi by adding device parameters and placed the driver in kernel-3.18/driver. But it didn’t work out.

First think to check is whether you have got your own kernel running (try uname -a and check the build time and date) and that have been able to update your device tree correctly (look in /sys/firmware/devicetree and check that your changes can be found).

After that, please come back with a lot more detail: log messages, what you changes you actually made, what “didn’t work out” actually means (what did you expect to happen, what actually happened, etc, etc, etc).

The Device is loaded with Android 6.0. How can I check it?

I am willing to make a build of image using a custom device tree. I am trying to add new hardware using low speed connector. I have device driver for hardware. How to connect the hardware to low speed connector ports and specify it in device tree.