Integrate meta-seco-rockchip in oniro

manifests/default.xml:      Add new project meta-seco-rockchip
local.conf.sample:          Add seco-px30-d23 to MACHINE
bblayers.conf.sample:       Add meta-seco-rockchip layer to BBLAYERS
conf-notes.txt              Add seco-px30-d23 to supported machines
machines-and-flavours.yaml  Add linux-seco-px30-d23 and linux-seco-px30-d23-extra jobs
linux-flavour.rst:          Add seco-px30-d23 to supported machines
machines-and-flavours.rst   Add linux-seco-px30-d23 job
boards/index.rst            Add seco-px30-d23 to supported boards

Add the seco-px30-d23.rst file representing the new Seco's JUNO board (SBC-D23) in the oniro project.

closes #156 (closed), #159 (closed), #160 (closed), #162 (closed), #163 (closed)

.oniro-ci/machines-and-flavours.yaml

@@ -131,6 +131,17 @@ linux-seco-imx8mm-c61-4gb-extra-gcc:
 linux-seco-imx8mm-c61-4gb-extra-clang:
   extends: [.linux-seco-imx8mm-c61-4gb-extra, .toolchain-clang, .broken]
 
+.linux-seco-px30-d23:
+  extends: .build-wic-image
+  variables:
+    CI_ONIRO_BUILD_FLAVOUR: linux
+    CI_ONIRO_RECIPE_NAME: oniro-image-base
+    MACHINE: seco-px30-d23
+linux-seco-px30-d23-gcc:
+  extends: [.linux-seco-px30-d23, .toolchain-gcc]
+linux-seco-px30-d23-clang:
+  extends: [.linux-seco-px30-d23, .toolchain-clang]
+
 .linux-raspberrypi4-64:
   extends: [.build-wic-image, .check-abi]
   variables: