Scott Ksander

Thanks for the tips.  The following overlay works on a c2
 
/dts-v1/;
/ {
        compatible = "amlogic,meson-gxbb";
        fragment@0 {
            target-path = "/aliases";
            __overlay__ {
                i2cA = "/soc/bus@c1100000/i2c@8500";
            };
        };
        fragment@1 {
            target-path = "/soc/bus@c1100000/i2c@8500";
            __overlay__ {
                #address-cells = <1>;
                #size-cells = <0>;
                pcf8563: rtc@51 {
                    compatible = "nxp,pcf8563";
                    reg = <0x51>;
                    status = "okay";
                };
            };
        };
};

Turns out the secret was getting the address and symbols right in the device tree.   I create the following as meson-pcf8563.dts, compiled into meson-pcf8563.dtbo, moved to /boot/dtb/amlogic/overlay, and added pcf8563 to the "overlays" line in armbianEnv.txt.
 
/dts-v1/;
 
/ {
            compatible = "amlogic,meson-gxbb";
 
            fragment@0 {
                  target-path = "/aliases";
 
                  __overlay__ {
                        i2cA = "/soc/bus@c1100000/i2c@8500";
                  };
            };
 
            fragment@1 {
                  target-path = "/soc/bus@c1100000/i2c@8500";
 
                  __overlay__ {
                        #address-cells = <1>;
                        #size-cells = <0>;
                        pcf8563: rtc@51 {
                              compatible = "nxp,pcf8563";
                              reg = <0x51>;
                              status = "okay";
                        };
                  };
            };
};