CODEOWNERS: Add Xilinx ZynqMP platform codeowner

Add @stephanosio as a code owner for the Xilinx ZynqMP platform, which
is used as the primary testing platform for the Cortex-R architecture.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>
diff --git a/CODEOWNERS b/CODEOWNERS
index e84a466..5012518 100644
--- a/CODEOWNERS
+++ b/CODEOWNERS
@@ -42,6 +42,7 @@
 /soc/arm/ti_simplelink/cc13x2_cc26x2/     @bwitherspoon
 /soc/arm/ti_simplelink/cc32xx/            @vanti
 /soc/arm/ti_simplelink/msp432p4xx/        @Mani-Sadhasivam
+/soc/arm/xilinx_zynqmp/                   @stephanosio
 /soc/xtensa/intel_s1000/                  @sathishkuttan @dcpleung
 /arch/x86/                                @andrewboie
 /arch/nios2/                              @andrewboie @wentongwu
@@ -83,6 +84,7 @@
 /boards/arm/nucleo*/                      @erwango
 /boards/arm/nucleo_f401re/                @rsalveti @idlethread
 /boards/arm/qemu_cortex_a53/              @carlocaione
+/boards/arm/qemu_cortex_r*/               @stephanosio
 /boards/arm/qemu_cortex_m*/               @ioannisg
 /boards/arm/sam4e_xpro/                   @nandojve
 /boards/arm/sam4s_xplained/               @fallrisk
@@ -244,7 +246,7 @@
 /dts/riscv/riscv32-litex-vexriscv.dtsi    @mateusz-holenko @kgugala @pgielda
 /dts/arm/armv7-r.dtsi                     @bbolen @stephanosio
 /dts/arm/armv8-a.dtsi                     @carlocaione
-/dts/arm/xilinx/                          @bbolen
+/dts/arm/xilinx/                          @bbolen @stephanosio
 /dts/xtensa/xtensa.dtsi                   @ydamigos
 /dts/xtensa/intel/                        @dcpleung
 /dts/bindings/                            @galak