feat: cite the handheld systems that run retroarch

One row per system the installer detects RetroArch on, with the card folder and the devices each system's own pages list, every value carrying its source. Android and Linux handhelds become tiles of the handheld group.

platforms/_guides.yml

@@ -63,6 +63,17 @@ device_groups:
       uses: retroarch
       runs_on: Android
       folder: '`RetroArch/system/` on the internal storage'
+    # Kinds of handheld that run a setup of their own: a tile each beside the
+    # setups of the group, leading to where their folder is written.
+    tiles:
+    - name: Android
+      # goretroid.com/products/retroid-pocket-5-handheld: "OS: Android 13".
+      # ayntec.com/products/ayn-odin-3: "Android 15".
+      text: Retroid, AYN Odin and other Android handhelds
+      link: platforms/retroarch.md#where-the-files-go
+    - name: Linux handhelds
+      text: ArkOS, muOS, Onion, spruceOS
+      link: platforms/linux-handhelds.md
   fpga:
     label: MiSTer FPGA
     description: >-
@@ -114,6 +125,89 @@ terminals:
       `bios` folder after `--dest`.
     shell: sh
 
+# The guide for the handheld systems that run RetroArch, one row for each
+# system the installer detects it on (_registry.yml, retroarch install.detect).
+# A folder is the one seen on the card from a computer, and a device list the
+# one the system's own site, wiki or README gives. Each is written only with
+# the first-party page that states it (`*_source`), and left out when no such
+# page states it: the row then says the command finds the folder.
+handheld_guide:
+  page: linux-handhelds
+  title: Linux handhelds
+  uses: retroarch
+  summary: >-
+    ArkOS, muOS, Onion, spruceOS and the other systems below run **RetroArch**, an app
+    with a small emulator for each console. They use its BIOS files.
+  systems:
+  - name: ArkOS
+    folder: '`bios` on the **EASYROMS** part of the card'
+    folder_source: https://github.com/christianhaitian/arkos/wiki/ArkOS-Emulators-and-Ports-information
+    devices: [RG353M, RG353V, RG503, RGB30, RK2023, RG351MP, RG351V, R35S, RGB10]
+    devices_source: https://github.com/christianhaitian/arkos/wiki
+  - name: muOS
+    folder: '`MUOS/bios` on the card'
+    folder_source: https://github.com/MustardOS/internal/blob/main/share/web/tools/bios-checker.html
+    devices: [RG35XX H, RG35XX Plus, RG35XX SP, RG35XX 2024, RG34XX H, RG40XX H, RG40XX V,
+              RG28XX H, RGCUBEXX, TrimUI Brick, TrimUI Smart Pro]
+    devices_source: https://muos.dev/devices
+  - name: Onion
+    folder: '`BIOS` at the root of the card'
+    folder_source: https://onionui.github.io/docs/emulators
+    devices: [Miyoo Mini, Miyoo Mini+]
+    devices_source: https://github.com/OnionUI/Onion
+  - name: spruceOS
+    folder: '`BIOS` at the root of the card'
+    folder_source: https://github.com/spruceUI/spruceOS/wiki/10.-Adding-BIOS
+    devices: [Miyoo A30, Miyoo Flip, Miyoo Mini, Miyoo Mini Plus, Miyoo Mini Flip,
+              TrimUI Smart Pro, TrimUI Brick, Anbernic RG35XX Plus, RG40XX H, Powkiddy RGB30]
+    devices_source: https://github.com/spruceUI/spruceOS/wiki/Supported-Devices
+  - name: Allium
+    devices: [Miyoo Mini, Miyoo Mini Plus, Miyoo Mini Flip]
+    devices_source: https://github.com/goweiwen/Allium
+  - name: Anbernic stock firmware
+  - name: ArchR
+    folder: '`/storage/roms/bios`, on a part Windows and macOS cannot open'
+    folder_source: https://arch-r.io/docs/roms/
+    devices: [R36S, R33S, R36S Soysauce, Odroid Go Advance, Odroid Go Super, RG351V,
+              RG351M, GameForce Chi, MagicX XU10, Powkiddy RGB10, Powkiddy RGB10X, K36]
+    devices_source: https://github.com/archr-linux/Arch-R
+  - name: CrossMix-OS
+    folder: '`BIOS` at the root of the card'
+    folder_source: https://github.com/cizia64/CrossMix-OS/wiki/Emulators
+    devices: [TrimUI Smart Pro]
+    devices_source: https://github.com/cizia64/CrossMix-OS
+  - name: dArkOS
+    folder: '`bios` on the **EASYROMS** part of the card'
+    folder_source: https://github.com/christianhaitian/dArkOS/wiki/dArkOS-Emulators-and-Ports-information
+    devices: [Odroid Go Advance, RGB10, RG351MP, G350]
+    devices_source: https://github.com/christianhaitian/dArkOS/wiki
+  - name: JELOS
+  - name: KOLOS
+    devices: [RG353P, RG353M, RG353V, RG353VS, RG503, Powkiddy RK2023, RGB30, RGB10 Max 3]
+    devices_source: https://github.com/AnonLinuxOS/KOLOS
+  - name: Koriki
+    folder: '`BIOS` at the root of the card'
+    folder_source: https://github.com/Rparadise-Team/Koriki/wiki/En:-02.-Content-installation
+    devices: [Miyoo Mini]
+    devices_source: https://github.com/Rparadise-Team/Koriki
+  - name: MiyooCFW
+    devices: [BittBoy, Pocket Go, PowKiddy Q90, PowKiddy V90, PowKiddy Q20 Mini, Sup M3, XYC Q8]
+    devices_source: https://github.com/MiyooCFW/docs/blob/main/docs/index.md
+  - name: plumOS
+    folder: '`bios` on the **PLUMOS** part of the card'
+    folder_source: https://github.com/game-de-it/plumOS-XU20V32/blob/main/docs/developer/storage-and-updates.md
+    devices: [MagicX XU20 V32]
+    devices_source: https://github.com/game-de-it/plumOS-XU20V32
+  - name: RetroOZ
+    devices: [OGS, OGA, RGB10Max, RGB10Max2]
+    devices_source: https://github.com/southoz/RetroOZ/wiki
+  - name: UnofficialOS
+    folder: '`roms/bios` on the games card'
+    folder_source: https://github.com/RetroGFX/UnofficialOS/wiki/Emulators-and-Game-Engines
+    devices: [R35S, R36S, RG351M, RG351P, RG351V, RG353M, RG353P, RG353V, RG503, RG552,
+              RGB30, RGB20 Pro, Odroid Go Advance, Odroid Go Super]
+    devices_source: https://github.com/RetroGFX/UnofficialOS/wiki
+
 guides:
   retroarch:
     summary: >-