Device tree compiler not recognizes C syntax for include files

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.preprocesseddtc -I dts -O dtb -p 0x1000 meson-gxl-s905x-khadas-vim.dts.preprocessed -o kvim1.dtbkvim1.dtb: Warning (unit_address_vs_reg): Node /scpi/clocks/scpi_clocks@0 has a unit name, but no reg propertykvim1.dtb: Warning (unit_address_vs_reg): Node /soc/bus@c8100000/pinctrl@14 has a unit name, but no reg propertykvim1.dtb: Warning (unit_address_vs_reg): Node /soc/periphs@c8834000/rng has a reg or ranges property, but no unit namekvim1.dtb: Warning (unit_address_vs_reg): Node /soc/periphs@c8834000/pinctrl@4b0 has a unit name, but no reg propertykvim1.dtb: Warning (unit_address_vs_reg): Node /soc/periphs@c8834000/eth-phy-mux has a reg or ranges property, but no unit namekvim1.dtb: Warning (unit_address_vs_reg): Node /gpio-keys-polled/button@0 has a unit name, but no reg propertykvim1.dtb: Warning (simple_bus_reg): Node /soc/bus@c8100000/pinctrl@14 missing or empty reg/ranges propertykvim1.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 propertykvim1.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.tdb4359446 -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.