How to integrate my own hardware drivers to Nios II project?

You need a <component>_sw.tcl script file.

Place it in the same directory as the SOPC Builder generated <component>_hw.tcl file

Some of the information in this file is used to specify the c/c++ source files and the include files. It also specifies such things as whether the component is auto initialized at boot-up (you have to write the code in your driver to do that), the minimum compatability versions, etc.

When generating a bsp, if you don't have this file for your component, it doesn't know where to look. Thus, your code will not be compiled into the bsp package.

Either find one already on your computer and modify it, or search for more help on Altera's website regarding writing HAL drivers.