Reserved-memory over multi banks

Question

I've got 2 banks of SDRAMs. Each of them is 4 GB. I'm going to reserve a piece of memory, which is from 0xb800_0000 to 0x1_8000_0000. How can I compose the reserved-memory node? Do I have to put it into 2 sub-nodes:

reserved-memory {
    #address-cells = <2>;
    #size-cells = <2>;

    foo: buffer@0xb8000000 {
        no-map;
        reg = <0x0 0xb8000000 0x0 0x48000000>;
    };

    bar: buffer@0x100000000 {
        no-map;
        reg = <0x1 0x0 0x0 0x80000000>;
    };
}

Or

reserved-memory {
    #address-cells = <2>;
    #size-cells = <2>;

    foo: buffer@0xb8000000 {
        no-map;
        reg = <0x0 0xb8000000 0x0 0xC8000000>;
    };
}