Add support for Xiaomi MIX 2S

data/devices/xiaomi/05_other.yml

@@ -74,6 +74,49 @@
     pixel_format: RGBA_8888
     theme: portrait_hdpi
 
+- name: Xiaomi Mi Mix 2S
+  id: polaris
+  codenames:
+    - polaris
+  architecture: arm64-v8a
+
+  block_devs:
+    base_dirs:
+      - /dev/block/bootdevice/by-name
+      - /dev/block/platform/soc/1d84000.ufshc/by-name
+    system:
+      - /dev/block/bootdevice/by-name/system
+      - /dev/block/platform/soc/1d84000.ufshc/by-name/system
+      - /dev/block/sde48
+    cache:
+      - /dev/block/bootdevice/by-name/cache
+      - /dev/block/platform/soc/1d84000.ufshc/by-name/cache
+      - /dev/block/sda20
+    data:
+      - /dev/block/bootdevice/by-name/userdata
+      - /dev/block/platform/soc/1d84000.ufshc/by-name/userdata
+      - /dev/block/sda21
+    boot:
+      - /dev/block/bootdevice/by-name/boot
+      - /dev/block/platform/soc/1d84000.ufshc/by-name/boot
+      - /dev/block/sde45
+    recovery:
+      - /dev/block/bootdevice/by-name/recovery
+      - /dev/block/platform/soc/1d84000.ufshc/by-name/recovery
+      - /dev/block/sda19
+
+  boot_ui:
+    supported: true
+    flags:
+      - TW_QCOM_RTC_FIX
+    graphics_backends:
+      - fbdev
+    brightness_path: /sys/class/leds/lcd-backlight/brightness
+    max_brightness: 4095
+    default_brightness: 2047
+    pixel_format: RGBA_8888
+    theme: portrait_hdpi
+
 - name: Xiaomi MIPAD 1
   id: mocha
   codenames: