docs(amiga): complete AmigaOS 3.1/3.2 developer reference — 172 files across 17 sections

Comprehensive technical documentation covering:
- Hardware: OCS/ECS/AGA custom chip registers, Copper & Blitter deep dives
- Boot sequence: cold boot through startup-sequence
- Binary format: HUNK executable spec, relocation, debug info
- Linking & ABI: .fd files, LVO tables, register calling conventions
- Exec kernel: tasks, interrupts, memory, signals, semaphores
- AmigaDOS: file I/O, FFS/OFS layout, CLI/Shell scripting
- Graphics: planar bitmaps, Copper programming, HAM/EHB modes
- Intuition: screens, windows, IDCMP, BOOPSI
- Devices: trackdisk, SCSI, serial, timer, audio, keyboard
- Libraries: utility, expansion, IFFParse, locale, ARexx
- Networking: bsdsocket API, SANA-II, TCP/IP stack comparison
- Toolchain: GCC, vasm/vlink, SAS/C, NDK, debugging
- Reverse engineering: IDA/Ghidra setup, compiler fingerprints, case studies
- CPU & MMU: 68040/060 emulation libs, PMMU, cache management
- Driver development: SANA-II, Picasso96/RTG, AHI audio

All files include breadcrumb navigation. No local paths or proprietary content.

10_devices/serial.md

@@ -0,0 +1,54 @@
+[← Home](../README.md) · [Devices](README.md)
+
+# serial.device — RS-232 Communication
+
+## Overview
+
+`serial.device` provides buffered RS-232 serial I/O through the Amiga's built-in 8520 CIA UART (active-high active sense).
+
+---
+
+## Opening
+
+```c
+struct IOExtSer *ser = (struct IOExtSer *)
+    CreateIORequest(port, sizeof(struct IOExtSer));
+OpenDevice("serial.device", 0, (struct IORequest *)ser, 0);
+```
+
+---
+
+## Setting Parameters
+
+```c
+ser->io_CtlChar   = SER_DEFAULT_CTLCHAR;
+ser->io_RBufLen   = 4096;       /* read buffer size */
+ser->io_Baud      = 9600;
+ser->io_ReadLen   = 8;          /* data bits */
+ser->io_WriteLen  = 8;
+ser->io_StopBits  = 1;
+ser->io_SerFlags  = SERF_XDISABLED; /* no XON/XOFF */
+ser->IOSer.io_Command = SDCMD_SETPARAMS;
+DoIO((struct IORequest *)ser);
+```
+
+---
+
+## Commands
+
+| Code | Constant | Description |
+|---|---|---|
+| 2 | `CMD_READ` | Read bytes |
+| 3 | `CMD_WRITE` | Write bytes |
+| 5 | `CMD_CLEAR` | Clear buffers |
+| 8 | `CMD_FLUSH` | Abort pending requests |
+| 9 | `SDCMD_QUERY` | Get status (bytes in buffer, errors) |
+| 10 | `SDCMD_BREAK` | Send break signal |
+| 11 | `SDCMD_SETPARAMS` | Set baud/bits/parity/stop |
+
+---
+
+## References
+
+- NDK39: `devices/serial.h`
+- ADCD 2.1: serial.device autodocs