Implement the MemoryRegion::subregions_description() handler to
be able to display the inverleaved memory regions:

  $ qemu-system-sh4 -M none -monitor stdio \
    -device mmio-testdev,address=0x00000000 -monitor stdio
  address-space: memory
    0000000000000000-ffffffffffffffff (prio 0, i/o): system
      0000000000000000-000000001fffffff (prio 0, i/o): testdev
        0000000000000000-00000000000007ff (prio 0, ram): testdev-sram
        0000000010000000-0000000017ffffff (prio 0, i/o): interleaver-container
          0000000011608000-00000000116081ff (prio 0, i/o): interleaver-16x8
          0000000011608000-00000000116081ff (prio 0, i/o):   8-bit access on 'sram-p0'
          0000000011608000-00000000116081ff (prio 0, i/o):   8-bit access on 'sram-p1' (8-bit shifted)
          0000000013208000-00000000132083ff (prio 0, i/o): interleaver-32x8
          0000000013208000-00000000132083ff (prio 0, i/o):   8-bit access on 'sram-p0'
          0000000013208000-00000000132083ff (prio 0, i/o):   8-bit access on 'sram-p1' (8-bit shifted)
          0000000013208000-00000000132083ff (prio 0, i/o):   8-bit access on 'sram-p2' (16-bit shifted)
          0000000013208000-00000000132083ff (prio 0, i/o):   8-bit access on 'sram-p3' (24-bit shifted)
          0000000013216000-00000000132161ff (prio 0, i/o): interleaver-32x16
          0000000013216000-00000000132161ff (prio 0, i/o):   16-bit access on 'sram-p0'
          0000000013216000-00000000132161ff (prio 0, i/o):   16-bit access on 'sram-p1' (16-bit shifted)
          0000000016408000-00000000164087ff (prio 0, i/o): interleaver-64x8
          0000000016408000-00000000164087ff (prio 0, i/o):   8-bit access on 'sram-p0'
          0000000016408000-00000000164087ff (prio 0, i/o):   8-bit access on 'sram-p1' (8-bit shifted)
          0000000016408000-00000000164087ff (prio 0, i/o):   8-bit access on 'sram-p2' (16-bit shifted)
          0000000016408000-00000000164087ff (prio 0, i/o):   8-bit access on 'sram-p3' (24-bit shifted)
          0000000016408000-00000000164087ff (prio 0, i/o):   8-bit access on 'sram-p4' (32-bit shifted)
          0000000016408000-00000000164087ff (prio 0, i/o):   8-bit access on 'sram-p5' (40-bit shifted)
          0000000016408000-00000000164087ff (prio 0, i/o):   8-bit access on 'sram-p6' (48-bit shifted)
          0000000016408000-00000000164087ff (prio 0, i/o):   8-bit access on 'sram-p7' (56-bit shifted)
          0000000016416000-00000000164163ff (prio 0, i/o): interleaver-64x16
          0000000016416000-00000000164163ff (prio 0, i/o):   16-bit access on 'sram-p0'
          0000000016416000-00000000164163ff (prio 0, i/o):   16-bit access on 'sram-p1' (16-bit shifted)
          0000000016416000-00000000164163ff (prio 0, i/o):   16-bit access on 'sram-p2' (32-bit shifted)
          0000000016416000-00000000164163ff (prio 0, i/o):   16-bit access on 'sram-p3' (48-bit shifted)
          0000000016432000-00000000164321ff (prio 0, i/o): interleaver-64x32
          0000000016432000-00000000164321ff (prio 0, i/o):   32-bit access on 'sram-p0'
          0000000016432000-00000000164321ff (prio 0, i/o):   32-bit access on 'sram-p1' (32-bit shifted)

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 hw/misc/interleaver.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/hw/misc/interleaver.c b/hw/misc/interleaver.c
index 46099e9e11..5cedcb3541 100644
--- a/hw/misc/interleaver.c
+++ b/hw/misc/interleaver.c
@@ -112,6 +112,34 @@ static MemTxResult interleaver_write(void *opaque,
     return r;
 }
 
+static GStrv interleaver_subregions_description(const MemoryRegion *mr)
+{
+    InterleaverDeviceState *s = container_of(mr, InterleaverDeviceState, iomem);
+    InterleaverDeviceClass *idc = INTERLEAVER_DEVICE_GET_CLASS(s);
+    gchar **descs = g_new(gchar *, idc->mr_count + 1);
+    unsigned output_access_bits = idc->output_access_size << 3;
+    size_t i;
+
+    for (i = 0; i < idc->mr_count; i++) {
+        if (i) {
+            descs[i] = g_strdup_printf("  %u-bit access on '%s'"
+                                       " (%zu-bit shifted)",
+                                       output_access_bits,
+                                       s->mr[i] ? memory_region_name(s->mr[i])
+                                                : emtpy_mr_name,
+                                       i * output_access_bits);
+       } else {
+            descs[i] = g_strdup_printf("  %u-bit access on '%s'",
+                                       output_access_bits,
+                                       s->mr[i] ? memory_region_name(s->mr[i])
+                                                : emtpy_mr_name);
+        }
+    }
+    descs[i] = NULL;
+
+    return descs;
+}
+
 static void interleaver_realize(DeviceState *dev, Error **errp)
 {
     InterleaverDeviceState *s = INTERLEAVER_DEVICE(dev);
@@ -139,6 +167,7 @@ static void interleaver_realize(DeviceState *dev, Error **errp)
     }
     memory_region_init_io(&s->iomem, OBJECT(s), &idc->ops, s,
                           idc->name, s->size);
+    s->iomem.subregions_description = interleaver_subregions_description;
     sysbus_init_mmio(SYS_BUS_DEVICE(s), &s->iomem);
 }
 
-- 
2.26.2