question: Multiple mcp23s08 on one chip-select with OF

Introduction:
Multiple mcp23s08 can be accessed individually with the same
chip-select when they have different addresses configured. They are configured as one spi-slave and there is one spi-chip created for each mcp23s08.

My Question:
How can I reference a single mcp23s08 gpio-chip in my device-tree. When
I use the of-handle of the spi-slave, I only reference the first mcp23s08.

Best Regards
Michael