diff --git a/src/SUMMARY.md b/src/SUMMARY.md
index df4d4de..d290d55 100644
--- a/src/SUMMARY.md
+++ b/src/SUMMARY.md
@@ -1,5 +1,6 @@
-[PSI Spec Introduction](intro.md)
-[Mask ROMs and Loaders](mask-roms-loaders.md)
-[Platform Initialization](platform-initialization.md)
-[Boot Environments](boot-environments.md)
-[Platform Security](platform-security.md)
+- [PSI Spec Introduction](intro.md)
+- [Mask ROMs and Loaders](mask-roms-loaders.md)
+    - [Rockchip](rockchip.md)
+- [Platform Initialization](platform-initialization.md)
+- [Boot Environments](boot-environments.md)
+- [Platform Security](platform-security.md)
diff --git a/src/rockchip.md b/src/rockchip.md
new file mode 100644
index 0000000..501ce10
--- /dev/null
+++ b/src/rockchip.md
@@ -0,0 +1,24 @@
+# Rockchip
+
+## RK3588
+
+The boot ROM uses the internal 12-bit 1MS/s SARADC to read `SARADC_IN0_BOOT` on
+power. It selects a boot mode based on the following table:
+
+| ADC value | Voltage | Mode |
+|-----------|---------|------|
+|         0 |       0 | USB  |
+|       682 |     0.3 | SD card, USB |
+|      1365 |     0.6 | eMMC, USB |
+|      2047 |     0.9 | FSPI M0, USB |
+|      2730 |     1.2 | FSPI M1, USB |
+|      3412 |     1.5 | FSPI M2, USB |
+|      4095 |     1.8 | FSPI M2, FSPI M1, FSPI M0, eMMC, SD card, USB |
+
+It will search each device in the order listed above for a valid image.
+
+`SARADC_IN0_BOOT` is often routed to a button, which when pressed is connected
+to ground (i.e. 0 V) and otherwise is 1.8V.
+
+Additional channels of the ADC may be routed to jumper headers to be used by
+later boot loader stages.