The regular toolchains from any vendor may not allow you to do this natively.

This is how it was done in the days of DOS/CPM based systems with limited memory.

You have the basic OS structure with fixed entry points(hooks) to various functions that your applications may need to access/handle the peripherals. This will be a fixed table of fixed hooks(pointers to functions who are placed at fixed addresses).

The application would then call these hooks at run time; of course, since they are at fixed addresses, it does not matter to the linker building the application.

Examine this

Your core driver (permanently resident) has these functions
0000 - pointer to LCD function(void)
0002 - pointer to Keyboard function(void)
...
...
000x - pointer to some other function(void)

LCD_function:
Kbd_function:
Other_function:

The application works something like this.
You may need to pass parameters in a set of global registers to / from the functions since the functions will be void of parameters and return values.

I am not 100% sure of the syntax shown below, but I use it as a guide to illustrate what I am saying.

#define  LCD_Hook  (*(code *)0000)
#define  KBD_Hook  (*(code *)0002)

main()
{
  LCD_Hook;    // call the lcd routine
  while (1)
  {
    Kbd_Hook;  // call the keyboard scanner
  }
}

I have given a divergent view, but I do hope it will be helpful.

Jerson