Restructure documentation

Move all extra documentation files into doc/ and move reverse
engineering related notes to a separate directory, to keep things tidy.

doc/reverse-engineering/stc12a-options.txt

@@ -0,0 +1,61 @@
+Model-specific configuration registers
+Placement of configuration values
+
+"~" means the bit is a negated boolean. Sometimes values overlap,
+depending on MCU model.
+
+In STC12A series, the first 7 MCS bytes have active
+values. Generally, unused bits should be set to 1.
+
+MCS0
+----
+
+MSB     7       6       5       4       3       2       1       0       LSB
+                                                        CLKSRC
+
+CLKSRC := clock source (0 = internal RC, 1 = external crystal)
+
+
+MCS1
+----
+
+MSB     7       6       5       4       3       2       1       0       LSB
+                        ~WDEN           ~WDSTP  WDPS2   WDPS1   WDPS0
+
+~WDEN := watchdog enable after power-on-reset
+~WDSTP := stop watchdog counter in idle mode
+
+WDPS2   WDPS1   WDPS0   divisior
+0       0       0       2 
+0       0       1       4
+0       1       0       8
+0       1       1       16
+1       0       0       32
+1       0       1       64
+1       1       0       128
+1       1       1       256
+
+
+MCS2
+----
+
+MSB     7       6       5       4       3       2       1       0       LSB
+                                                        ~EERE   ~BSLD
+
+~EREE := enable eeprom erase next time MCU is programmed
+~BSLD := enable BSL pin detect; i.e. BSL is only enabled if P1.0/P1.1
+         (or others, depends on MCU model) are held low on POR.
+
+
+
+MCS3 (at index 6!)
+------------------
+
+MSB     7       6       5       4       3       2       1       0       LSB
+                LVD
+
+LVD := low voltage detection threshold
+
+LVD     threshold
+0       3.7V
+1       3.3V