This is not a Device Tree syntax issue, you just have to pre-process the .dts file with the C preprocessor, cpp, in order to obtain a file that can be digested by the Device Tree Compiler as is.
In your specific case, assuming your current directory would be the kernel root directory, you would have to use the two following commands:
cpp -nostdinc -I include -I arch -undef -x assembler-with-cpp arch/arm64/boot/dts/amlogic/meson-gxl-s905x-khadas-vim.dts meson-gxl-s905x-khadas-vim.dts.preprocessed
dtc -I dts -O dtb -p 0x1000 meson-gxl-s905x-khadas-vim.dts.preprocessed -o kvim1.dtb
kvim1.dtb: Warning (unit_address_vs_reg): Node /scpi/clocks/scpi_clocks@0 has a unit name, but no reg property
kvim1.dtb: Warning (unit_address_vs_reg): Node /soc/bus@c8100000/pinctrl@14 has a unit name, but no reg property
kvim1.dtb: Warning (unit_address_vs_reg): Node /soc/periphs@c8834000/rng has a reg or ranges property, but no unit name
kvim1.dtb: Warning (unit_address_vs_reg): Node /soc/periphs@c8834000/pinctrl@4b0 has a unit name, but no reg property
kvim1.dtb: Warning (unit_address_vs_reg): Node /soc/periphs@c8834000/eth-phy-mux has a reg or ranges property, but no unit name
kvim1.dtb: Warning (unit_address_vs_reg): Node /gpio-keys-polled/button@0 has a unit name, but no reg property
kvim1.dtb: Warning (simple_bus_reg): Node /soc/bus@c8100000/pinctrl@14 missing or empty reg/ranges property
kvim1.dtb: Warning (simple_bus_reg): Node /soc/periphs@c8834000/rng simple-bus unit address format error, expected "0"
kvim1.dtb: Warning (simple_bus_reg): Node /soc/periphs@c8834000/pinctrl@4b0 missing or empty reg/ranges property
kvim1.dtb: Warning (simple_bus_reg): Node /soc/periphs@c8834000/eth-phy-mux simple-bus unit address format error, expected "55c"
Verifying kvim1.dtb was built:
ls -ail kvim1.tdb
4359446 -rw-rw-r-- 1 user user 27568 Jun 2 12:05 kvim1.dtb
For the official Device Tree specification, please refer to its official web site and its git repository.